64 Bulletin Vanderbilt Marine Museum, Vol. VI 



Technical description : The carapace is three-fifths as wide 

 as long, convex from side to side, with the postorbital horns strong, 

 upstanding, procurved, projecting above and beyond the eyes; 

 laterally compressed, acuminate, with a small strong acute pair of 

 spines immediately behind the rostral spines. There is a small 

 strong pair of spines near the frontal border and in line with the 

 spines on the upper margin of the antennal peduncle, these repre- 

 sent the postorbital spine ; a similar pair of spines, but placed on 

 the frontal margin, represent the antennal spine. Behind each the 

 rostral, postorbital and hepatic spines there are in approximate 

 longitudinal series, rows of much smaller, acute, forward-directed 

 spines, and interspersed between these, especially in the median 

 postcervical area, there are other small spines or blunt tubercles. 

 A series of small spines ornament the posterior border of the 

 thorny portion of the carapace; immediately behind this area 

 there is a deep, wide, smooth, curved groove, which in turn is 

 bordered posteriorly by the flat, wide carina, with its anterior 

 margin ridged and finely setose, that defines the posterior border 

 of the carapace, and is continuous at its postlateral angles with 

 a similar slightly narrower carina and groove that border the lat- 

 eral margins of the carapace. The cervical groove is deep and 

 wide, especially in the median dorsal line, and curves forward on 

 the inferolateral area, terminating almost at the frontal margin 

 behind the outer side of the antennal peduncle. The cardiac region 

 is clearly defined, the urogastric sulcus being deeper and forming 

 a deep sulcus on either side. 



The orbital segment is thick, with the anterior margin convex, 

 a median distal tuft of fine hairs on the upper margin. The stalk 

 is heavily calcareous, maculated like the carapace, produced on 

 the anterior lateral border into a denticle-like process, margined 

 by short setae; just beyond this process the stalk is constricted 

 near the base of the cornea and produced into a rounded calcareous 

 process on the upper surface. The cornea is subspherical, large, 

 with an excellent visual range in all directions. The rostral segment 

 is large, being one-half as long as the precervical portion of the 

 carapace, as wide proximally as long, with the outer margin widely 

 convex, thickened ; there are two pairs of submedian spines on the 

 dorsal surface, the anterior pair being slightly the larger and 

 placed practically on the margin ; the second pair being a short 

 distance behind these and anterior to the center of the segment. 



