; N 



STOMAPODA. 



STOMAPODA. 



910 



along the internal border of their second joint ; there is also a small 

 rudimentary palpiform appendage. The second pair of jaws are 

 lamellar, nearly triangular, and composed of four or five joints placed 

 end to end ; nothing resembling a flabelliform appendage is to be seen. 

 The members which belong to the seventh cephalic ring, and which 

 ordinarily constitute the anterior jaw-feet, do not seem to belong to 

 the buccal apparatus. They are very much elongated, and form a 

 pair of slender feet, generally enlarged towards the end, the uses of 

 which are not known. 



M. Milne-Edwards divides' this family into two small tribes, 

 Eriehthians and Squillian?. 



Tribe 1. Erichthiaiis. [EMCHTHUS.] 



Tribe 2. Squillians. 



Corresponding with the genus Squilla of Fabricius, and the majority 

 of authors, this tribe comprehends, according to M. Milne-Edwards, 

 the genera Squilla (containing the Stjuilla, properly so called), Gono- 

 dactylut, and Coronis of Latreille. All these crustaceans have, 

 observes M. Edwards, the greatest resemblance to each other, and 

 the differences upon which these genera are established have not 

 perhaps as much importance as was once thought. 



The Squillians are, of all the podophthalinous crustaceans, those 

 in which the various constituent rings of the body are the most 

 equally developed and the most independent of each other. With 

 the exception of those which immediately surround the mouth, all 

 these rings are more or less moveable on each other, and the greater 

 part are complete. The carapace neither covers the first two rings 

 of the head nor the last four rings of the thorax, and constitutes a 

 horizontal buckler nearly quadrilateral, which is divided longitudinally 

 into three lobes, more or less distinct, by two longitudinal furrows. 

 In front of this buckler is a small triangular and moveable plate, 

 which seems to be a dependence of it, and which covers the anteu- 

 nular ring ; its form varies, and as it may be an element in specific 

 differences, M. Milne-Edwards terms it the frontal plate. The ring 

 which carries the eyes is small, nearly quadrilateral, and moveable on 

 the succeeding segment ; the eyes ara large, short, and convex. The 

 antennular ring is also nearly quadrilateral and moveable, but larger, 

 and gives insertion to the internal antennae by its anterior border on 

 each side of the ophthalmic ring. These appendages are directed 

 forwards ; their peduncle is long, slender, and composed of three 

 cylindrical joints, and they terminate in three multiarticulate fila- 

 ments of moderate length. The second pair of antennas are inserted 

 under the anterior border of the carapace, on each side of the anten- 

 nular ring, and are formed nearly the same as in the Erichthians ; the 

 first joint of their peduncle is large and short, and continues itself 

 with an articulation equally stout, which carries at its extremity a 

 great oval blade, analogous to the palp or middle branch of the 

 thoracic limbs, and the basilary scale of the external antennae of the 

 shrimps ; the internal branch, which ordinarily is greatly developed, 

 remains here slender, and so small that it only seems to be an 

 appendage of the middle branch ; it springs from the anterior angle 

 of the common basilary joint, and presents a peduncular portion, 

 composed of two cylindrical joints and of a terminal multiarticulate 

 filament. 



The internal structure of the Squillians differs considerably from 

 that of the Decapods. The heart, instead of being quadrilateral, and 

 inclosed in the middle part of the thorax, has the form of a long vessel, 

 rather enlarged anteriorly, which extends nearly throughout the length 

 of the abdomen as well as of the thorax, and which furnishes laterally 

 in each of the rings which it traverses a pair of arterial branches ; by 

 its anterior extremity, this dorsal vessel gives origin to three branches, 

 which seem to be the analogues of the ophthalmic and antennary 

 arteries of the Decapods; and posteriorly it terminates by a small 

 artery which penetrates into the last abdominal segment. 



The stomach is very large, and advances into the head very far 

 before the cesophagus, which is vertical and extremely short. 



The organs of generation are situated above the digestive apparatus. 

 The nervous system presents nearly the same disposition as in the 

 greater portion of the Macrourous Decapods ; in the abdomen the 

 ganglions are well developed, and the cords double ; it is the same 

 with the thoracic ganglions of the three last pairs, but all those of the 

 anterior portion of the thorax are united in a single oval mass. 



ffjuilla (Rondeletius). M. Milne-Edwards points out that the true 

 fyuiltiai are probably more carnivorous than the other crustaceans o 

 this tribe, for they are furnished with much more powerful offensive 

 arms. The claw which terminates their raptorial feet has a falcular 

 form, the sharp edge of which is provided with long pointed teeth 

 and can be received into a groove of the corresponding border of the 

 hand, which ia equally compressed, and in general armed with spine. 

 on its piehensile border. The three last pairs of thoracic feet carry a 

 slender, cylindrical, and elongated appendage, which represents the 

 palp. The body is in general more slender and narrowed behind the 

 carapace than in the other Hquillians. 



Squilla: are found in the British Channel, but the species which are 

 numerous are abundant only in the seas of warm regions ; they kee] 

 in general at a distance from the coast, and at considerable depths 

 Their abdominal false feet are continually in motion, and they swim 

 with great swiftness, striking the water with their powerful tail. 



Squilla, seen from above. 



M. Milne-Edwards divides the true Squillce into two sub-genera : 

 1, Squilles Fines-Tallies; and, 2, Squilles Trapues. 



1. Slender Squilla. 



The species arranged under this sub-genus are remarkable for the 

 narrowing of the posterior portion of their thorax and the gradual 

 enlargement of the abdomen. The sub-genus is divided by M. Milne- 

 Edwards into the following sections : 



a. Species whose abdomen presents above neither crests nor 

 large tubercles, and has its last segment twice and a half 

 as wide as it is long ; rounded and hardly deutilated. 

 8. maculata. Length from 10 to 12 inches. It inhabits the Asiatic 

 seas. 



(8. Species whose abdomen preseuts above many longitudinal 

 crests, or large elongated tubercles, and has its last segment 

 ill general nearly as long as it is wide. 



* Rostral plate not covering the ophthalmic ring. 

 S. Mantis. Length 6 or 7 inches and upwards. It is found in the 

 Mediterranean. 



** Rostral plate entirely hiding the ophthalmic ring. 



S. Ftrutsaci. Length about 4 inches. It is found on the coasts of 

 Sicily. 



2. Stout Squillce. 



This sub-genus has the body very convex, all of a size, without any 

 notable narrowing at the back part of the carapace. 



S. stilifera. Length about 3 inches. It is a native of the island 

 of Mauritius. 



Gonodactylus (Latreille). The principal distinction of this genus 

 from the last group lies in the mode of conformation of the raptorial 

 feet. The last joint of these organs, in lieu of having the form of the 

 claw lamellar and strongly dentated, is straight, styliform, more or 

 less convex at its base, and presents at most only vestiges of teeth 

 on its prehensile border, which is enlarged. In general the convexity 

 of the basilary portion is very considerable, and suffices to distinguish 

 these crustaceans at the first glance. 



* Rostral plate armed on the median lino with a long spiuiform 



tooth. 



0. CJiiragra. Length about 3J inches. The species are found in nil 

 the seas of warm climates : the Mediterranean, American coasts, Sey- 

 chelles Islands, near Trincomaloe, and Tongataboo. 



