1921 J Schmitt: The Marine Decapod Crustacea of California 25 

 Gennadas pectinatus, sp. nov. 



Plate 11, figure 1 



Fig. 12. Gennadas pectinatus; thelyeum. 



Description. — Rostrum slightly ascending, with a styliform apex, and armed 

 above with two slender teeth, of which the posterior is situated just above the 

 posterior margin of the orbit and the anterior just behind the middle of the 

 rostrum; the rostrum exceeds the eyes by one-half the length of that portion lying 

 anterior to the anterior dorsal spine; dorsal carina continued backward as far as 

 the cervical groove, behind which the dorsal surface of the carapace is smooth and 

 rounded; at the antero-lateral sinus is a sharp marginal spine. Eyes apparently 

 devoid of pigment; tubercle on inner angle of somewhat flattened eyestalk, small 

 and blunt. Spine of antennal scale falls short of the extremity of the blade by 

 nearly the width of the blade at the end of the spine; antennular peduncle 

 reaching a little beyond middle of antennal scale. Endopodites of external or 

 third maxillipeds broken off. Palm and fingers of first pair of chelipeds subequal 

 in length; of the second pair the palm is about four-fifths the length of the 

 fingers. 



Thelyeum as figured (fig. 12), a hastate, medially carinated plate between the 

 bases of the fourth pair of legs, a curved spine between the third pair, and a more 

 or less rectangular pubescent area between the last pair of legs. 



Exopodites of first abdominal appendages as long as distance from tip of 

 rostrum to posterior margin of first abdominal segment, including carapace; 

 between the bases of these appendages there is a thickened triangular plate with 

 a blunt, forwardly-direeted apex. Fifth and sixth abdominal segments carinated, 

 carina of fifth ending in a small, sharp spine, which projects beyond the posterior 

 margin of the segment. Sixth segment more than twice as long as the fifth, with 

 posterior end partly broken away; it may have ended in a spine like the fifth. 

 There is a small spine at the postero-ventral angle of the sixth segment, and a 

 large one at the postero-dorsal angle of the epimeron of the fifth. Fourth abdom- 

 inal segment armed on the posterior margin with a peculiar comb-like structure, 

 a series of pectinations beginning with a few denticles just above the epimeron, 

 which increase in size and become spine-like toward the median line, forming there 

 quite conspicuous teeth which in the type specimen are as much as one and one-half 

 millimeters long. Outer blade of uropods exceeding the inner by about one-third 

 of their length; telson with four pairs of lateral spines, tip broken. 



Dimensions. — Type, female: length of carapace and rostrum 41 mm., of abdo- 

 men to extremity of broken telson 74 mm. 



Type Locality. — Known only from a single female specimen (Cat. No. 53329, 

 U.S.N.M.), dredged by the "Albatross" in 1350 to 2182 fathoms, off Santa 

 Catalina Island, California (station 4390). 



Remarks. — This species differs, so far as I am aware, from all known species 

 of Gennadas in the peculiar armature of the posterior margin of the fourth 

 abdominal segment. 



