REPORT ON THE CRUSTACEA MACRURA. 



635 



The pleon is smooth. The third somite is slightly gibbous but not produced to a 

 tooth. 



The telson is laterally armed with four small spines on each side, and is subequal in 

 length with the outer plates of the rhipidura. 



Habitat.— Station 207, January 16, 1875; lat. 12° 21' N., long. 122° 15' K; offTablas 

 Island; depth, 700 fathoms; bottom, blue mud; bottom temperature, 51°"6. One 

 specimen. Trawled. 



This species may easily be distinguished .from the others by the general smoothness of 

 the carapace and pleon. There are only two lateral carinas, but neither of them is very 

 pronounced, only forming slight longitudinal elevations. The upper lateral carina 

 commences just within the orbital margin, traverses the hepatic region, and then ascends 

 in a curved line, approaching but not quite reaching the posterior margin ; it coincides 

 with the upper lateral carina in Heterocarpus carinatus. The carina, which in 

 Heterocarpus carinatus is confluent with the tooth that stands on the frontal margin at 

 the outer canthus of the orbit, is wanting, the elevation ending a little below the upper 

 carina. The carina which commences at the second antennal tooth corresponds with the 

 lower carina in Heterocarpus carinatus ; in this species it is prominent anteriorly, but 

 gradually loses its importance, and ceases before it reaches the posterior margin of the 

 carapace. The dorsal carina is strongly elevated over the gastric region, where it is 

 armed with six large subequal teeth ; a seventh, not quite so large, stands on the rostrum 

 anterior to the eyes, and two others, equally distant from each other and from the apex, 

 stand on the upper margin of the rostrum, which is laterally compressed and obliquely 

 elevated. The lower margin is armed with twelve teeth, all sharp and anteriorly directed, 

 and gradually diminishing in size as they approach the apex. 



The pleon is smooth and without any armature, but the third somite is elevated in the 

 median line to a longitudinal ridge or tuberosity that gives it a gibbous appearance. 



The telson (fig. 2z) is dorsally flattened and laterally compressed at the margins, and on 

 each side the longitudinal angle formed by the lateral compression is armed with four small 

 spines, and the extremity is fringed with four, of which the two outer are the larger. 



The ophthalmopoda are orbicular, of moderate size, and projected upon a short and 

 slender pedicle. 



