and Species of Macrurous Crustaceans. 63 



blanched like the rest of the appendages; but in life the delicate 

 rose-pink coloration of the animal extended itself to their very- 

 tips. The peduncles are far less conspicuous from the side 

 view than represented in the plate. 



The first pair of abdominal appendages, those which bear 

 the great chela;, are unfortunately absent, the specimen having 

 lost its claws a considerable period previously to its capture, as 

 the presence of uncalcified reproduced rudiments of these 

 appendages indicates ; the other legs are smooth and slender : 

 the second and third pairs are didactyle ; of these the former 

 has both its upper and lower margins, from the base of the 

 carpopodite to the extremity of the claws, fringed with long 

 hairs ; the latter, much the slenderer as well as the longer of 

 the two, has its propodite greatly elongated, and its claws are 

 ciliated : the fourth pair, the longest of all and ciliated only 

 on the outer face of the dactylopodite, and the fifth, about as 

 long as the second pair, are monodactyle. 



The last abdominal somite is immovably united to that 

 which precedes it, as in Nephro2>s and the common lobster*; 

 and the sternum is linear, as in the Astacidce generally. 



Postabdomen. — The postabdomen is gradually attenuated 

 to the extremity of the telson. The appendages of its first 

 somite are as completely rudimentary as they are in the female 

 of Nephrons norvegicus^; those which follow are long and 

 slender, their foliaceous branches being very narrow, produced 

 to a sharp point, and fringed with excessively long cilia. All 

 the terga are covered with minute rounded tubercles, and present 

 at their anterior ends,just behind the tergalfacets, abroadsmooth 

 transverse groove, with its hinder margin convex backwards. 



The pleuron of the first somite is precisely similar to that of 

 Nephrops norvegicus ; but those of the remaining somites are 

 even more acutely triangular than in that species, and have 

 their margins denticulate and furnished with a fringe of long 

 cilia. In all the somites, with the single exception of the first, 



* On characters furnished hy the claws alone Dana artificially divides 

 the recognized genera of Astacidce into two groups, typified respectively 

 by Astacus and Nephrops ; the first of these is further subdivided according 

 to the number of the branchiae and the mobility or immobility of the last 

 abdominal somite ; but no mention is made of the fact that this is firmly 

 fixed in Nephrops too. If Paranephrops, a genus including only fresh- 

 water forms, should turn out to have a mobile last abdominal somite, then 

 we shall have this curious fact presented to us — viz.,that all those members 

 of the family Astacidte which live in fresh water or are terrestrial (ttigceus) 

 have this somite movably united by membrane only to that which pre- 

 cedes, while those of them tbat are marine have it fixedly united to the 

 rest of the sternum. 



t The ventral plates of the 2nd, 3rd, and 4th postabdominal somites in 

 the males of Nephrops norvefficus have an erect spine in the middle line ; 

 but the females exhibit no trace of such. 



