110 



Its range, is seen by glancing al the extent of country that is embraced in 

 its wanderings. It is common on the coasts of France and En^hind ; it 

 is found in the Baltic Sea, along the shores of the Mediterranean, and 

 in the Red Sea. It is by no means an uncommon crab along the whole 

 extent of the eastern coast of the United States, and Heller records it 

 as coming from the shores of Brazil. 



I am able to detect some differences, amounting probably to a slight 

 geographical variation, among the specimens coming from these widely 

 separated localities. Those from the American coast differ from the 

 European in having a slight increase in the convexity of the carapace, 

 with coarser granulations over its surface. The teeth of the front are 

 also much more prominent. In the European specimens the projections 

 of the front hardly amount to more than undulations; while in those 

 from this side they are teeth-like. An increased development in the 

 same direction is observed in the individual from the Hawaiian Islands. 

 If what I have stated here should hold good through a large series of 

 specimens, it will be an interesting instance of progressive development 

 from east to west, where the difference in the local conditions are less 

 pronounced than from north to south in corresponding degrees of 

 longitude. 



ASSECLA, 7WV. gen. 



Carapace convex, broader than long, smooth and shining; front 

 broad, produced, broadly triangular; anterolateral and posterolateral 

 borders nearly equal in length ; the latter converging posteriorly ; an- 

 tero-lateral border five-lobed; hiatus at the internal angle of the orbit 

 completely closed by a process from the base of the external antenna; 

 the movable part of the antenna excluded from the hiatus; a process 

 from the front descends to meet the process from the base of the exter- 

 nal antenna. The third joint of the external maxillipeds longer than f^i 

 broad at the base; broader at the base than at the apex, irregularly 

 quadrilateral; inner angle of the base somewhat projecting. A prom- 

 inent ridge on the palate ; the ridge is not jiroduced to the anterior 

 margin of the buccal area. Basal article of the external antennae large, 

 nearly longitudinal. Arm not projecting beyond the carapace; hand 

 short, carinated ; tarsus of the posterior pair of legs flattened, subovate, 

 or lanceolate-ovate; very slightly modified into a swimming apparatus. 



In respect to the development of its natatorial feet this genus bears 

 the same relation to Lissocarcinus, as Carcinus does to Platyonichus. 



