48 H. WOODWARD Otf NEW XIMMEEIDGE-CLAY MACRTTRA. 



• In 1868 I called attention to two new species of Callianassa at 

 the Norwich Meeting of the British Association* — one, the Callia- 

 nassa neocomiensis, from the Greensand of Colin Glen near Belfast, 

 the other, C. Batei, from the Upper Marine series (Eocene), Hemp- 

 stead, Isle of Wight. 



I have now, by the kindness of Mr. Henry Willett, F.G.S., and 

 the Committee of the Sub-Wealden Exploration, been favoured with 

 portions of cores from the boring obtained at a depth of 1057 feet, 

 containing, besides the fore limbs of a small macrurous Crus- 

 tacean, to be presently described, three or four more or less perfect 

 examples of a new species of Callianassa, and the oldest hitherto 

 known of this remarkable type of fossorial Crustaceans (PL VI. 

 figs. 1 & 2). 



The fossil, which measures about 42 mm. in length, is seen in 

 profile on several sections of cores, and indicates the horizontality 

 of the beds penetrated. The parts of the fossil are all in situ, save 

 the carapace, which has been displaced in each case. 



The first pair of feet, which are longer than the entire body, have 

 the penultimate joint, or manus, enormously developed (measuring 

 7 lines in length) ; the wrist is quadrate, broader than it is long ; 

 it decreases greatly in size from its broad articulation with the 

 manus to its narrow proximal end, where it joins the arm (or 

 " meros "), which is short and strongly curved, and is united by two 

 very small and extremely slender joints (the " ischium" and " basos ") 

 to the cephalothorax. 



The hands of the fore limbs are more equal in size than in the 

 living species of Callianassa ; but in other genera of Thalassinidse, 

 as for instance in Axius, the inequality is less marked. In the 

 Eocene and Cretaceous species (already referred to) the disparity in 

 the relative size of the hands is also somewhat diminished as com- 

 pared with existing species. I am therefore not disposed to lay much 

 stress upon this point. 



The feet of the second pair are also didactyle ; and the extremities of 

 all the four pairs of smaller limbs are somewhat flattened and ex- 

 panded, to assist in digging. 



The carapace and the segments of the abdomen are smooth ; the 

 latter are somewhat quadrate in profile, not pointed ; and the shelly 

 covering of both is extremely thin, as in all the forms which habi- 

 tually conceal themselves in foreign bodies — a peculiarity developed 

 in the highest degree in the Paguridse. The segments of the abdo- 

 men contract somewhat at each extremity as in other Callianassa} ; 

 and the caudal plates are oval. 



I propose to designate this new species Callianassa isochela. 



2. Mecochirus Peytoni, sp. nov. PI. VI. fig. 3. 



Kimmeridge Clay, Boulogne-sur-mer, and Sub-Wealden boring. 



I should have hesitated to describe the fossil macruran repre- 

 sented by the two small fore limbs preserved in one of the cores for- 



* Brit. Assoc. Eeport, Norwich, 1868, p. 72, pi. ii. figs. 4 & 5. 





