GALATHEA. CRUSTACEA. 163 



shell short, broad, and slightly depressed, with a pointed ros- 

 trum before ; abdomen long, of seven joints ; tail rounded. 



M. Moniagui, Leach. (C. rhomboidalis, Mont.) Rostrum entire, 

 terminated by a spine projecting forwards ; shell smooth poste- 

 riorly ; haunches of the first eight feet with a curved spine be- 

 low. 3 lines long. Coasts of Britain. Malac. Brit.^l. 16, fig. 1-6. 



Gen. 51. GALATHEA, Fab. Lat. Cancer, Lin. 

 Four antennae, the intermediate two short, with the last joint bi- 

 fid, the lateral ones long, setaceous, simple ; exterior feet-jaws 

 elongated, with the extremity of the two first joints spinous ; 

 rostrum short, spinous, or dentated ; body oblong; tail extend- 

 ed, sometimes bent, terminated with a lamellar fin ; anterior 

 pair of feet equal, elongated, tuberculous, and spinous, with 

 long toes, dentated at the extremity, and hollowed anteriorly ; 

 fifth pair of feet filiform ; abdomen folded under the body. 



G. strigosa, Fab. (Astacus, Pen.) Second joint of the exterior feet- 

 jaws shorter than the first ; forceps scaly and spinous above and on 

 the sides, with the toes compressed and toothed at the end ; ros- 

 trum long, with nine teeth j colour bright red or brown, and of a 

 brilliant blue at the junction of the segments. Inhabits Euro- 

 pean seas. Frequent on the coast near Edinburgh. Pen. Brit. 

 ZooL iv. pi. 15. 



Gen. 52. PORCELLANA, Lam. Cancer, Oliv. 

 Lateral antennae long, setaceous, and inserted on the exterior 

 side of the eyes, the intermediate ones lodged in two grooves ; 

 body orbicular, almost square, slightly flattened ; tail bent 

 below, with the margin ciliated, rarely furnished with appen- 

 dages at the end ; ten feet, the two anterior didactyle, the 

 posterior two very small. 



P. plaiycheles, Lam. Shell suborbicular, glabrous, granular, ter- 

 minated by three blunt tubercles ; forceps very large, triangu- 

 lar, flattened on the external side, which is strongly ciliated. In- 

 habits European seas. B Penn. Brit. Zool. iv. pi. 6, fig. 2. 



FAMILY VI. ASTACIN&. 



Four or six anterior feet didactyle ; exterior leaflet of the late- 

 ral appendages of the fin terminating the abdomen in some 

 entire, in others divided by a suture. 



Gen. 53. THALASSINA, Lat. Astacus, Herbst. 

 Exterior antennae of medium length, setaceous, with simple pe- 

 duncles ; internal stalk of the exterior feet-jaws composed of six 

 hairy joints, of which the first is longest and spinous; four 

 anterior legs didactyle, the first pair very large ; body elon- 

 gated ; tail long, subcylindrical, with the terminal fin small 

 and entire. 



