134 ELPIDIIDAE. 



Station 4651. Peru: west of Aguja Point, 111 miles. 2,222 fms. Bott. temp. 35.4°. Fne. stky. gy. m. 

 Station 4672. Peru: southwest of Palominos Light House, 88 miles. 2,845 fms. Bott. temp. 35.2° 

 Fne. dk. br. infus. m. 



Four specimens. 



Periamma tetramerum, 1 sp. nov. 

 Plate 2, fig. 4. 



Length, 50 mm.; diameter, 15 mm. Body-wall very thin and delicate. 

 Color, pale yellowish brown and grayish; the gray areas appear to be where the 

 brown is rubbed off. Tentacles ten. Pedicels, eight on each side, the most 

 anterior largest (2 mm. long or more), situated anterior to middle of body; 

 the posterior four smallest and more or less united together. About 12 mm. 

 back of anterior end is a transverse crest, 8-9 mm. wide and 4 mm. high, more 

 or less lobed, but not markedly so; this crest is apparently made up by the 

 fusion of two pairs of processes, i. e. four projecting papillae, and back of it, 

 there is on each side a similar papilla 1.5 mm. high. General appearance much 

 like a small Scotoplanes robusta. Internal anatomy completely indeterminable 

 owing to the whole interior being densely packed with mud. 



Calcareous particles very characteristic. In deeper layer of skin are 

 numerous C-shaped (sometimes S-shaped) bodies, 100 n long. External to these 

 is a layer of very diversified thorny spicules, generally tetramerous; each forms 

 a more or less perfect cross with two opposite arms shorter than the other two; 

 rarely the spicules are trimerous or pentamerous; each arm of a spicule is usu- 

 ally about 100 ix long but often they are less. Here and there among these 

 crosses are much stouter, thorny rods, 200-300 ll long; these often have a 

 short branch, at a right angle, on one side, near the middle. 



Station 4670. Peru: west of Palominos Light House, 105 miles; 3,209 fms. Bott. temp. 35.4°. Fne. 

 dk. br. m. 



Six specimens. 



These specimens seem to have suffered considerable damage in the ascent 

 of the trawl, for in the largest ones the outer spicule layer is nearly all rubbed 

 off leaving only the C-shaped particles. The dorsal crest is more or less dam- 

 aged but its form and size are fairly recognizable. The number, size, and 

 arrangement of the pedicels is also distinguishable in most of the specimens. 

 The spicules are very characteristic and there will be no difficulty in recogniz- 

 ing examples of the species where enough of the epidermis is intact to permit 

 the existence of the crosses to be determined. 



1 rerpi.t'tpoi = having four parts, in reference to the characteristic spicules. 



