110 PORTUNID^. 



that they may be merely varieties ; although there are 

 certain comparative characters which, as they are pretty 

 constant, render it necessary that further investigations 

 should be made before their identity can be fully es- 

 tablished. Then the whole contour of the animal is 

 more strongly marked in the present species ; the mar- 

 ginal teeth are more prominent ; the margins of the 

 orbit more distinctly granulated ; the latero-posterior mar- 

 gin much more contracted and more deeply emarginate at 

 the angles ; the outer carina of the hand, more strongly 

 denticulate ; and the terminal joint of the posterior feet 

 rounder and broader in proportion to its length. In other 

 respects the similarity is so great in the form of all the 

 parts, as fully to justify Dr. Milne Edwards's remark of 

 their " extreme resemblance." It is matter of surprise that 

 Dr. Leach should not have observed this close relation of 

 these two species ; but that he should, on the contrary, have 

 stated that P. lividus [holsatus] most nearly resembles P. 

 depurator, a species from which, in fact, it differs most ob- 

 viously. It is remarkable that the specimens of P. mar- 

 nioreus in the British Museum, which were collected by Dr. 

 Leach, differ much more from holsatus, than those which I 

 have myself procured; the hand having in all those imarmed 

 carina?, and the upper margin of the orbit without granula- 

 tions. The figures in Dr. Leach's beautiful work, also 

 magnify the distinctions far beyond the truth. 



The occurrence of this Crab is extremely rare on our 

 coasts ; Dr. Leach mentions his having found a single spe- 

 cimen amongst a number of P. depurator that were taken 

 in the Frith of Forth at Newhaven, and that he observed 

 another in the collection of Montagu ; but there is a 

 fine series in the British collection of the British Museum, 

 which must have been procured after the " Malacostraca 



