Euchotomera, with two species typica and tenuis from the Pacific, agrees with Erythrops in the form of the very short, lamellar, unincised telson. The scale of the second antennæ is smooth on the outer margin. The legs are very slender. Some of the joints of the legs, the pleopods in both sexes, and the uropods, are fringed with long setæ, from which circumstance it may be supposed that the generic name is derived, meaning 'with the parts beautifully hairy.' Professor Chun comments on the astonishing length of the upper antennæ in the type species, which he regards as a transitional form between Mysis and his own Arachnomysis Leuckartii.

Siriella, Dana, was originally named Cynthia, by Vaughan Thompson, but the name was preoccupied, and Dana's Siriella takes precedence of White's Cynthilia. The genus is characterised chiefly by the structure of the legs, 'which are more decidedly unguiculate than in any other known genus of Mysidans,' and have the sixth joint entire or subdivided into two articulations only; also by the pleopods of the male, which are natatory, and have the 'basal lobe of inner branch usually transformed into two gill-like, more or less spirally twisted stems.' The outer branch of the uropods is broader than the inner, and has an imperfect articulation at the apex. The telson is elongate, densely spinose at the edges, with the apex not incised. The species are numerous, and many of them are met with at the surface of the sea, far from the coast. The British species, as far as at present known, are: 1. Siriella norvegica, Sars, in which the third joint of the first antennæ has three setæ on the inner margin, and between the spines at the angles of the telson three spinules, of which the central is the largest. 2. Siriella Clausii, Sars, of which Norman gives the distinguishing characters as 'the single seta on inner margin of last joint of peduncle of antennules, the slender legs and claws, and three equal-sized spinules between the ultimate spines of the telson.' 3. Siriella jaltensis, Czerniavsky, identified by Norman with the later Siriella crassipes, Sars, in which the form is somewhat more robust and the legs much stronger than in the

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preceding species, while the telson terminates in a small spinule flanked on each side by the usual setæ, and a more minute spinule between the ultimate pair of spines.' 4. Siriella Brooki, Norman, which seems to be intermediate between Siriella Clausii and Siriella jaltensis, having the single antennular seta of the former, and the apex of the telson armed as in the latter, the legs also being of intermediate thickness. 5. Siriella armata (Milne-Edwards), which is distinguished by an elongate rostrum reaching the end of the second joint of the first antennæ, and by the telson 'terminating usually in four equal-sized spinules and two setæ between the ultimate spines.' In Norman's opinion both Mysis Griffithsiæ, Bell, and Mysis productus (Gosse) may be synonyms either of this or of the next species. Pseudosiriella, Claus, was instituted to receive the species Mysis frontalis, Milne-Edwards, which Sars had previously transferred to Siriella. It has a well-developed rostrum like Siriella armata, but the appendages, to which a branchial function has been attributed, on the pleopods of the male, are here simple instead of being coiled. According to Canon Norman, Pseudosiriella frontalis belongs to the British as well as the Mediterranean Fauna.

Gastrosaccus, Norman, is distinguished by the laterally compressed carapace, and in the female by the great development of the side-plates of the first pleon-segment which appear to assist the marsupium in the retention of the eggs. The marsupial plates are two pairs, the first pair being very small and sending a strap-shaped setiferous process into the cavity of the pouch. The first pleopods in the female are very large, the rest very small. All the pleopods of the male are biramous and at least in part natatory. The telson is apically incised. Gastrosaccus sanctus (van Beneden) is found in the Mediterranean, on the Belgian and French coasts, and at Jersey. Gastrosaccus spinifer (Goës) is found both in the Baltic and on the coasts of Great Britain, and is distinguished from the preceding species by the dentately fringed hind margin of the carapace and by a well-developed dorsal spine on the fifth pleonsegment.

Haplostylus, Kossmann, was established to receive the Mediterranean species, Gastrosaccus Normani, Sars, which is also found off the coast of Ireland, and a Red Sea species, Haplostylus erythraus, Kossmann, the generic distinction consisting in the absence of the forward directed lobes on the concave hinder rim of the carapace, which are found in the species of Gastrosaccus above mentioned, and also in the reduction to a rudiment of the inner natatory branch of the third pleopods of the male.

It will be seen from the foregoing notes that fifteen genera of this family are represented in the Fauna of Great Britain, and it is quite possible, and even probable, that extended research may show that others of the genera and species occur round the very varied coasts of the British Isles, which in their southern parts, especially if the Channel Islands are included, are in rather marked contrast to the region of the Orkneys and the Shetland Isles, among which Norwegian and Arctic forms may readily present themselves. It will be understood that, although an endeavour has been made to mention all the valid, or at least all the commonly accepted, genera of the Schizopoda, there are very numerous species belonging to those genera of which it has been impossible to take notice.

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CHAPTER XIX

SUB-ORDER IV.-STOMATOPODA

THE carapace is feebly developed, leaving uncovered at least the last three segments of the trunk; the pleon is powerful, and, like the carapace, usually depressed, not laterally compressed. The eyes are stalked. The second antennæ have a scale. The mandibles have a small or rudimentary 'palp.' The three pairs of maxillipeds and the two following pairs of appendages are variously modified as six-jointed prehensile limbs, with epipods, but without exopods; the second maxillipeds being predominant in size and importance. The three following pairs of legs are feebly developed, with exopods, but without epipods. The first five pairs of pleopods generally carry each a pair of large ramified branchia arising from the outer branch. There is a special apparatus on the inner branch of the first pleopods in the male. The caudal fan is powerful. The heart is elongate, with several pairs of lateral venous fissures. The ovaries and testes lie chiefly in the pleon, and have their two halves united by a median piece. There are no spermatophores. The spermatozoa are simple, rounded cells. The young are hatched not as Nauplii, but in a more advanced stage. The carapace of the young is largely expanded.

6

The above definition is chiefly taken from that given by Dr. J. E. V. Boas for the Order Squillacea,' in his highly esteemed 'Studies on the Relationships of the Malacostraca.' It is in this sub-order that the typical number of twenty-one segments has been distinguished in a single animal. Usually the first antennæ have three flagella, one of the two principal ones sending off a branch from

near its base. The ocular and antennal segments are more or less movable, and not covered by the carapace. The two pairs of maxillæ are rather simply constructed. The first of the two series of legs are closely applied to the mouth, and from this circumstance the sub-order has received its appellation of mouth-footed.' According to Professor W. K. Brooks, in his Report on the Challenger Stomatopoda, there are about sixty species known of adults, and an equal or greater number of larvæ, from the tropical, sub-tropical, and temperate waters of the Atlantic, Pacific, and Indian Oceans. Some of the species range over the whole of this area, while others are known from only a single restricted locality, almost a fourth of the species having been described from single specimens. They are usually found in very shallow water, only one or two species being reported from depths like a hundred and twenty fathoms. The wide distribution of many of the species is undoubtedly due to the great length of their larval life, during which they swim at the surface, and are swept to great distances by the oceanic currents.' On the other hand, the adults are extremely active in their movements and retiring in their habits, most of them being burrowing animals, from which it results that they may long remain undiscovered even in localities where they are abundant. Some, like Squilla empusa, which hunt far from their burrows, are often caught in nets and trawls, but others, such as Lysiosquilla excavatrix, are the Myrmeleons of the ocean, lying in wait for their prey, covered with sand, with only the tips of their eyes exposed, at the mouths of their very deep burrows, to the bottoms of which they dart at the least alarm.' At a station where they were extremely numerous, Professor Brooks could scarcely capture one, till he devised the insidious plan of holding bait in one hand and a trowel in the other at the mouth of the burrow, and even so with his best speed the trowel often cut in two the retreating quarry.