Am 



CRUSTACEOLOGY. 



51. Mysi? 



,?altatoriu< 



grustacea. in the month of August, in the greatest abundance. 



S -""V^ P ' The females were with young, and the males were more 

 abundant than the females. Like the foregoing species, 

 it swims with its head uppermost, having a most gro- 

 tesque appearance. Colour when alive, pellucid, cine- 

 reous, spotted with black and reddish-brown, varying 

 much in their position. Mr Leach confesses, that he did 

 not at first conceive it to be distinct from Praunusjlcxuo- 

 sus, but on examination found that they not only differ- 

 ed in size, but most essentially in the middle process of 

 the tail-fin. Length a third of an inch. 



Family XII. Souillarii. 



.50. Squjl- Genus L. Squilla. Interior antenna? with three 

 lA - articulated setie. Two large arms. Ten feet, with an 



hooked hand ; the other six simple. 

 Mantis. Sp 1. Mantis. Upper part of the body with several 



elevated longitudinal lines ; thumbs with six dents. 



Inhabits the Mediterranean and Asiatic seas. 



Cancer mantis of Linne. Astacus mantis of Pen- 

 nant ? Squilla mantis of Fabricius and Latreille. 



This species lias been introduced into the British 

 Fauna, but the authority is questionable. 



Genus LI. Mysis. Interior antennae with two arti- 

 culated seta?. Arms small. Twelve feet, all armed 

 with a claw, and formed for swimming. 



Sp. 1. Saltalorius. 



Cancer pedalus of Otho Fabriciu3. Mysis saltalorius 

 of Latreille. 



Inhabits the Greenland Sea. 



This genus is introduced from the Genera Tnscclorum 

 el Crnstaccormn of Latreille, who owns that he has ne- 

 ver examined the species himself, but has admitted it 

 into his work solely on the authority of Otho Fabricius. 



Family XIII. Gnathionii. 



Genus LII. Gnatiiia. Mouth with two strong por- 

 rected mandibules or jaws, concave above, convex be- 

 low. Antenna? setaceous; the upper pair rather longest. 

 Feet ten, all aimed with a nail. Tail jointed, and fur- 

 nished with a swimming tail, as in the family Asta- 



CINI. 



Sp. 1. Termitaides. Mandibules on the inner side 

 armed with minute teeth; middle process of the tail 

 triangular, apex acute. 



Cancer maxdlaris of Montagu. 



Gnatiiia teruiitoidts, Leach's MSS. 



Inhabits the British Ocean, but is not common. 



Mr Leach suspects, that Oniscus cceruleatus of Mon- 

 tagu, Lin. Trans, vol. xi. is the female of this animal. 



Family XIV. Gammarini. 



]. Superior antennae shorter than the peduncle of the 

 inferior antennas. Feet fourteen. 

 US. Tali- Genus LIII. Talitrus. Anterior pair of feet lar- 

 tkus. ger than the second pair; no hands. 



Observe. The animals of this genus are familiarly 

 known under the name of sand/toppers, and cannot have 

 escaped the observation of the most cursory observer, 

 multitudes being seen, during the summer, on all our 

 sandy shores, skipping about in all directions in the 

 evening. Their use in the economy of nature appears 

 to be that of contributing to the dissolution of putrid 

 animal and vegetable matter. 

 L«custa. Sp. 1. Locust n. Inferior antenna? as long as the bo- 



dy ; the last division with between thirty and forty 

 smaller joints. 



Cancer locust a of Pennant and Gmelin. Oniscus lo- 

 «usl« of Pallas. Gammarus locusta of Fabricius ? Can* 



Talitrus locusta of Ctu*i«ea 



S'2. Gka- 



TH1A. 



Tcrmitoi- 

 •ej. 



cer gammarus saltator of Montagu 

 Latreille. 



Inhabits the sandy shores of the European ocean. It 

 has acquired the name Is<cu*ia from the form of its 

 mouth, which is protruded, and very much resemble* 

 that part of a locust. Length three quarters of an inch. 

 Colour, when alive, corneous ; when dead, whitish, and 

 often mottled with reddish. It has never been taken 

 in the water ; it burrows in the sand, and serves as food 

 to the shore birds, who devour it with avidity. 



Sp. 2. Litoralis. Inferior antenna? much shorter 

 than the body, the last segment composed of about 

 twenty-five joints. 



Tali.hus Uttnralis. Leach's MSS. 

 Inhabits all the sandy shores of Britain. It was first 

 observed by the Rev. J. Fleming, who communicated 

 it to Mr Leach, from whose manuscripts it is here in- 

 serted. Length about half an inch. Colour corneous, 

 inclining to reddish on the back. It is so common, that 

 a more minute account is unnecessary, it having all the 

 habits of the preceding species. 



Genus LIV. Orciiestia. Two anterior pair fur- 

 nished with a moveable thumb, which is capable of be- 

 ing bent on the edge of the hand ; second pair largest, 

 having a compressed hand. 



Sp. 1. Littorea. Hand ovate, the part which meets 

 the thumb slightly toothed or wrinkled. Thigh of the 

 posterior pair of legs jointed, and very much compressed. 

 The female wants the hands. See Plate CCXXI. fig. 6. 

 Pulex marinus of Baxter ; Cancer gammarus liiloreus 

 of Montagu ; Orchcsles littorea, Leach's MSS. ; Tali- 

 trus gammarellus, Latreille ? 



This species is the only one of the genus hitherto dis- 

 covered. It is very common on many of our shores, 

 lurking under the rejectamenta of the sea, having all 

 the habits of the preceding genus. Latreille quotes Bax- 

 ter's figure, which renders it highly probable that this 

 may be his Talitrus gammarellus ; but as he quotes also 

 the Oniscus gannnarellus of Pallas, it still remains in 

 some doubt. 



2. Superior antenna? longer, or at least as long as the 

 inferior. Fourteen feet, the third and fourth pair 

 smallest. 

 Genus LV. Gammarus. The four anterior feet 

 furnished with a moveable nail, which is capable of be- 

 ing bent inwards on the hand. Abdomen with thirteen 

 joints. Peduncle of the antenna? with three joints. 



Observation. The animals composing this ^enus in- 

 habit ponds and rivulets, also the sea side. The males 

 are considerably larger than the females, which they 

 embrace with their claws, often swimming about with 

 them, and not unfrequently on their back. The females 

 carry about their young with them after their exclusion. 

 * Fresh water. 

 Sp. 1. Pulex. Eyes ovate, situated on a level with 

 the base of the superior antenna? ; back near the tail 

 with fasciculi of spines. 



Cancer pulex of Linne and Pennant ; Gammarus pulex 

 of Fabricius and Latreille. 



This species is utterly incapable of living in the sea, 

 although we have the authority of Linne and many of 

 his followers to the contrary ; the truth is, that Linne 

 included the various species of this genus under the 

 names Cancer locusta and Pulex; this shows the neces- 

 sity and advantage of constituting natural genera, the 

 only way by which we can ever hope to attain an ac- 

 curate knowledge of species. 



A species which Mr Leach considers as distinct 

 from pulex, was discovered in water taken from a 



Littoral!;. 



54. Os- 



CHESTIA. 



Littorea, 



fLATK 



CCXXf. 

 Fig. 6. 



55. Gax. 



MiitVf. 



Pulex. 



