24 BULLETIN OF THE 



rected forward, and on the posterior lobe with three more. The lateral margin, 

 behind the cervical suture, is armed with six to eight similar teeth, which 

 become successively more remote posteriorly. There is a slight median carina 

 extending the whole length of the carapax, and armed, behind the two rostral 

 spines, first with a single small spine directed forward, then with two side by 

 side and very close together, then with one, then with two on the posterior 

 edge of the cervical suture, then with two more, and finally with two some- 

 what larger and more widely separated spines projecting forward from the 

 anterior edge of the broad and prominently raised posterior margin. In front 

 of the cervical suture there is an in-egular longitudinal dorso-lateral line of five 

 minute spines each side, and back of these a single spine each side on the pos- 

 terior edge of the cervical suture. Extending from the posterior margin nearly 

 to the cervical suture, there is a sharp sublateral carina parallel to the lateral 

 margin, about a third of the way from it to the median carina, and armed with 

 five or six small spines. 



The ventral regions of the carapax (PI. IV. fig. 1) are inflected each side at 

 a very acute angle with the dorsal surface, and, the sternum being narrow, the 

 ventral regions are very broad. The ventral region each side is divided longi- 

 tudinally into three approximately equal parts by two prominent carinse ; the 

 outer carina (marking the pleurotergal suture ?) extends from the anterior 

 margin at the base of the antenna, in a slightly sinuous line, toward the posteio- 

 lateral margin of the carapax ; the anterior half is very prominent, and armed 

 with small spines directed outward, while the posterior half is much less con- 

 spicuous, unarmed, and disappears entirely before reaching the posterior angle 

 of the carapax. The inner carina extends along the branchial region from near 

 the base of the first leg quite to the postero-lateral angle of the carapax ; the 

 extreme anterior portion is not prominent, but from opposite the third leg 

 posteriorly it is very prominent, acute, and armed with ten to fifteen sharp 

 spines. The outer of the three longitudinal regions thus marked out is divided 

 transversely by the cervical suture, and the anterior portion (subhepatic region) 

 is divided transversely into an anterior and a posterior lobe by a groove nearly 

 or quite as conspicuous as the cervical. In the frontal margin of this anterior 

 lobe, and near its inner side, there is a deep sinus corresponding to the orbital 

 sinus of the dorsal surface, but not quite as wide, and open nearly to the dorsal 

 surface, except where it is crossed by a protuberance from the ventral portion 

 of the ophthalmic lobe. 



On the upper surface of the carapax, the orbital sinus, each side, is com- 

 pletely filled by the dorsal part of the ophthalmic lobe, of which the anterior 

 margin is slightly concave in outline and continuous with the anterior margin 

 of the carapax, but has a small tubercle near the middle. The dorsal surface 

 of the lobe is smooth, calcareous, and opaque, and on a level with the adjacent 

 surface of the carapax except posteriorly, where a small oval area of the ex- 

 tremity of the lobe is exposed by a depression in the carapax. This oval area 

 is thin, semitranslucent, and not calcareous, and has every appearance of being 

 a true corneal area, although I am unable to detect any evidence of facets. The 



