96 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 8 



Distribution. — Known from the type locality. 



Depth. — Dredged at 35-40 fms. 



Specimens examined. — The type. 



Remarks. — The type and other specimen measure 2 cm. in length 

 and 3 mm. in width. The surface of the skin appears mottled, because of 

 the large scales' being glassy and contrasting with the solid white of the 

 smaller spicules which are massed between them. The tentacles which 

 are completely retracted are small and finger shaped ; only 8 could be 

 counted, but 2 small ones may possibly have been overlooked. The cal- 

 careous ring is low with no indication of posterior prolongations; the 

 stone canal is small and attached as usual in the dorsal mesentery, and 

 the Polian vesicle is single and ventrally placed. Other anatomical fea- 

 tures are not remarkable. The gonads form few tubes of varying length, 

 and are attached near the middle of the dorsal midline. 



This species seems most closely related to L. imbricata (Semper) and 

 L. typica (Theel). It differs in having small biscuit-shaped plates in- 

 stead of rosettes in the external layer of the skin, fewer feet, and, presum- 

 ably, in having simple tentacles. However, L. nova, L. imbricata (and L. 

 typica) may well be placed in a separate genus for which the name 

 Parocnus is proposed, with imbricata as type. 



2. Leptopentacta panamica, new species 

 Plate 14, Figs. 6-12; text figure 2 



Diagnosis. — Slender form with curved body, ambulacra forming 5 

 indistinct ridges. Feet in scattered double rows in the middle portion of 

 the ambulacra, toward the ends in single rows, around the base of the 

 introvert forming 5 large valves as in Pentacta. Tentacles 10, bushy, 

 the 2 ventral smaller. Surface of skin rough on account of the numerous 

 spinelike projections on the spicules which pierce the skin. Calcareous 

 ring with short posterior prolongations. Other features also typical of 

 the genus. 



Spicules consisting of an external layer of strongly knobbed 4-holed 

 buttons with minute holes and smaller buttons, less strongly knobbed and 

 with larger holes and numerous 4-spoked baskets, and an inner layer of 

 large, reticulated ovoid or spherical scales or grains. Feet possibly with an 

 end plate (not discovered in type)^ and numerous perforated supporting 



4 The type species has a large and well-developed end plate in the feet (over- 

 looked by H. L. Clark), and one would expect that an end plate would also be 

 present in the present species. Two tube feet have been examined, but the feet 

 are strongly contracted and no trace has been found of end plates. Still it is pos- 

 sible that they may be present. 



