Boone, Crustacea, Cruise of "Alva," 19 SI 201 



Kemp, in similar scaphocerite and similar ornamentation of the 

 posterior four abdominal segments but again diifers in the cari- 

 nae on the carapace ; those of the present species have each only one 

 anterior spine, while on Mr. Kemp's P. incisus the carinae each 

 bear several spines; also P. vanderbilti has seven major carinae, 

 while P. incisus has only five major carinae. 



The rostrum is wider by one-fifth than one eye and is deeply 

 concave or trough-like from the orbital angle to the distal rostral 

 border, which appears linear, concave in a dorsal view, but in 

 reality has the tip bent down at an approximate right angle 

 and produced into a deep median lobe, which is distally widely 

 rounded, the distal lateral margin on either side of this deep 

 median lobe is shallowly convex, tapered toward the outer lateral 

 angle, giving the lower, or distal margin a trisinuate contour. 

 The orbital margin is subcarinate, separated by a small, supra- 

 orbital notch from the rostrum and the infraorbital angle is a 

 rounded process ; the anterolateral angle is an acute triangle. The 

 carapace is short and wide, median width about eighty-five per 

 centum of the length taken from tip of rostrum to posterior mar- 

 gin. There are seven primary carinae and two secondary carinae 

 present on the carapace. The median dorsal carina begins im- 

 mediately behind the base of rostrum as a short carina termi- 

 nating anteriorly in a single tooth; this short carina runs back 

 nearly one-fifth the length of carapace ; immediately behind it an- 

 other small tooth tips the remaining portion of the median carina, 

 which extends back almost to the hind margin. The uppermost 

 lateral carinae consist of a very short oblique pair near the pos- 

 terior margin, beginning slightly behind the cervical groove and 

 extending obliquely forward and outward, almost touching the 

 second pair of lateral carinae. The second pair of lateral carinae 

 are 1.5 times as long as pair I and lie obliquely between the 

 median dorsal line carina and pair III of the lateral carinae, 

 arising in a small tooth about one-third of the distance from the 

 posterior margin of carapace and near the median dorsal carina 

 and extending obliquely almost to the anterior end of lateral 

 carinae pair III. Lateral carinae pair III arise near the posterior 

 margin and extend forward about two-thirds of the length of 

 carapace, terminating in an acute small tooth which is slightly 

 posterior to the second tooth of median carina. The lateral carinae 

 pair IV are the shortest of the entire series and quite oblique; 



