264 Messrs. J. Wood- Mason and A. Alcock on 



This species was taken near the same place in a previous 

 season. 



Family Leucosiidae. 

 45. Parilia Alcocki, gen. et sp. n., Wood-Mason. 



This crab is remarkable not only for the great size to whicli 

 it attains — equalling though not exceeding the Myropsis 

 goliuth of A. Milne-Edwards — but also for the great develop- 

 ment of the respiratory mechanism. The finely and sharply 

 granulated carapace is distinctly broader than long. When 

 viewed from above it appears hexagonal in outline, the in- 

 terval between the outer canthi of the afferent branchial 

 apertures forming the wide and straight anterior side ; the 

 intervals between the outer canthus of the afferent branchial 

 apertures and the last antero-lateral tooth of each side, the 

 nearly straight antero-lateral sides ; the intervals between the 

 last antero-lateral tooth and the posterior branchial spine of 

 each side, the very strongly arched postero-lateral sides ; and 

 the interval between the posterior branchial spines of opposite 

 sides, the posterior side of the hexagon. It is depressed in 

 front and strongly swollen behind^ both vertically and hori- 

 zontally, but especially horizontally, so as in a side view to 

 appear wedge-shaped. The regions are well-marked, the 

 n)uch inflated branchials being sliarply marked off from the 

 elongated ^er«r-c?e-/?/s-shaped gastro-cardiac and from the 

 lupatics by a deep groove, which, conmiencing behind the 

 cardiac protuberance, passes forwards and inwards, and then 

 curves boldly forwards and outwards to the first antero-lateral 

 tooth on each side, and is deeply indented at intervals in its 

 course. The hinder margin bears three short conical spines, 

 of whicli the middle is small and tends to degenerate with 

 age into a mere clump of granules. Above the marginal 

 spines, on the vertical hinder surface, is a transverse row of 

 three similar spines, of which two are on the branchial 

 regions and the third and smallest arises from the middle of 

 the cardiac boss, whence a carina passes forwards along the 

 mid-dorsal line nearly to the frontal margin. The antero- 

 lateral margin bears four spiniform tubercles, one in the 

 middle of the length of the pterygostomian ridge (which, in 

 the absence of an hepatic ridge, functions as a portion of the 

 antero-lateral margin), and three separated from each other 

 by equal intervals and from the pterygostomian by an interval 

 equal to the sum of their own interspaces. 



The two antennulary lubes of the front, which is much as 



