t 

 4 PROCEEDINGS OF THE 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 

 existing species of our coast ((7. irvoraUis and C. borealis), being 

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

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

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

 well-marked, more or less flattened, bosses 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 papillai 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 front there are two small tuberosi- 

 ties, situated 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 are perfectly preserved ; they correspond to the second 

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

 (corresponding to the tliird tooth in C. irroratus) is straight on the 

 free edge, with about 15 papillas 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 the edge and near it are 

 almost exactly the same in number, size, and position as in C. irroratus. 



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

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

 oblique row extending to the insertions of the hinder pair of legs, are 

 almost exactly as in the existing species. In the fossil species there 

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

 the same number in C. irroratus, at a point near the median line 

 of the carapace; while in the middle of the series there are five, but 

 in G. irroratus only three, being slightly larger and farther apart. 



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

 the legs, and I can detect no good specific differences. In the sternum 

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

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



