4 PROCEEDINGS OF Tin: AMERICAN ACADEMY. 



Carapace entire, with the exception of the greater part of the front 

 margin. It is much higher and much more convex than in the two 

 iting Bpecies of our coast (('. irroratus and G. borealis), being 

 almost rounded, the convexity being between one-fourth and one-third 

 the entire thickness of the body. The surface is much more irn g- 

 ular than in the two existing Bpecies, being thrown up into fourteen 

 well-marked, more or less flattened, hosses or tuberosities. Of these, 

 four are .situated along the median line; the one most posterior is the 

 broadest and highest, the fourth or most anterior one the smallest and 

 lowest ; also the granulations or crateriform papilla) covering the sur- 

 face of all the tuberosities are larger and more prominent than those 

 elsewhere on the surface of the carapace. On each side of the median 

 row are five other flattened low tuberosities, the largest of which is 

 opposite the second median one (counting from behind), and half-way 

 between this and the outer side of the same tuberosities is a small one ; 

 behind the one first named is a small one situated opposite to the first (or 

 most posterior ) median tuberosity. In frout there are two small tuberosi- 

 ties, Bituated opposite the anterior median one, but placed a little nearer 

 the front edge, and directly behind the orbit or base of the eyestalk; of 

 these two bosses the outer one is the larger. 



Fortunately on the left side of the left orbit two of the marginal teeth 

 of the carapace arc perfectly preserved ; thej correspond to the second 

 and third teeth, from the left orbit, of C. irroratus. The third tooth 

 (corresponding to the third tooth in ('. irroratus) is straight on the 

 free edge, with about lo papilla; or granulations along the edge, while the 

 other (the second) is more conical or tooth-like, with from 16 to 18 

 granulations; indeed the granulations on tho edge and near it are 

 almost exactlj the same in number, Bize, and position as in C. irroratus. 



The hinder edge of the carapace is much as in C. irroratus ; the row 



granulations on each Bide of the middle of the carapace, and the shorter 



oblique row extending to the insertions of the hinder pair of le_ r s. are 



almost exact!) as in the existing Bpecies. In the fossil Bpecies there 



are about four of these granulations to the millimetre, there being 



the Bame number in 0. irroratus, at a point near the median line 

 of the carapace; while in the middle of tin- Beries there are five, but 

 in 0. irroratus only three, being -lightly larger and farther apart. 



The Bternum is as in the male 0. borealis, as are the basal joints of 

 the legs, and F can detect do good specific differences. In the Bternum 

 of the fossil the three segments, including the apical one, 



which ends at the insertion of the maxillipeds. are well preserved. 



