362 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 22, 



of the eyes is preserved, and appears to be spherical, and about half 

 a line in diameter. 



There is no appearance to indicate any prolongation of the front 

 edge into a rostrum ; nor are there any portions of the antennee 

 remaining. The posterior edge of the carapace is also emarginate (to 

 receive the first segment of the abdomen); the ridges end abruptly 

 upon it, without being produced into any spines or prolongations. 



With the exception of an oblong tumidity on either side of the 

 anterior end of the median ridge, there are no punctations, tubercula- 

 tions, or sculpturings. 



Abdominal segments. — Of the abdomen, which is rather depressed, 

 four segments only are visible, measuring in all two lines in length ; 

 but the probability is, that the remainder are concealed in the matrix. 

 In all those present, the articular facet is smooth, but the posterior 

 portion of the first segment is elevated, and covered with small tuber- 

 culations, and in the succeeding segments it has a median ridge and 

 lateral prominences corresponding to those upon the carapace (fig. 2). 



In the second segment, the epimeraare smooth and unornamented, 

 and bent down at right angles to the tergum, which presents a peculiar 

 ornamentation. In each half of the tergum there are two transverse, 

 triangular elevations ; the base of the larger and anterior one corre- 

 sponding with the lateral ridge, the apex being connate with the cen- 

 tral ridge ; while in the posterior triangle, the base constitutes the 

 hinder portion of the median ridge and the apex of the outer ridge ; 

 each of these elevations is tuberculated, and the spaces between them 

 are smooth. The remaining segments present slight modifications, 

 but are essentially similar (fig. 1, c). 



The carapace is not overlapped by the first segment. 



Limbs. — The few portions of limbs remaining are fragmentary. 

 They are subtrigonal and several times longer than broad. 



Locality, — The specimen under notice was found in a coprolitic 

 mass from the Lias bone-bed at Aust Passage. 



Affinities. — Although the carapace, in consequence of its flatness 

 and the production of its posterior angles, presents a facies not very 

 dissimilar from that of some Stomapods, such as certain species of the 

 genus Ericthys, the general characters of the specimen are those of a 

 Decapod ; for it differs from the Stomapods in possessing a deep cervi- 

 cal furrow, extending right across the carapace, and dividing it into 

 a cephalic and a scapular portion. This character does not occur, so 

 far as I am aware, in any of the Stomapods ; nor on comparing it with 

 the recent species of this group, can I find any of these with the 

 abdomen similarly ornamented. 



Turning next to the four great divisions of the Macrura, I think 

 that we may at once exclude that of the Thalassinidce, containing such 

 genera as Callianidea and Thalassimis, in which the slender and com- 

 piessed abdomen, the slight integument, &c. are characters directly 

 opposed to those of our specimen. 



In three families of the division termed by M. Milne-Edwards 

 " les Salicoques," viz. the CrangonidcB, the Alpheidce, and the Palce- 

 monidcey there is no distinct cervical groove, while in the fourth, the 



