48 CAITLOPHACUS SCHULZEI. 



Caulophacus schulzei Wilson. 

 Plate 7, figs. 20-31; Plate 8, figs. 1-29; Plate 9, figs. 1-33; Plate 10, figs. 1-29; Plate 11, figs. 1-17. 

 Mem. M. C. Z., 1904, 30, p. 43; Plate 4, figs. 1, 3, 5-10; Plate 5, figs. 1-6, 8-10. 



All the specimens referred to this species were trawled at Station 4651 off 

 northern Peru on 11 November, 1904; 5° 41.7' S. 82° 59.7' W. ; depth 4063 m. (2222 

 f.); they grew on sticky, fine, gray sand; the bottom-temperature was 35.4°. 



Apart from peculiarities due to differences of age and preservation, all 

 these sponges are fairly identical. The nearly complete specimens are mush- 

 room-shaped, composed of a discoid body and a stalk attached to the lower 

 face of the disc. The fragments appear to be parts of similar sponges. Six 

 specimens have been selected for detailed study, and to these all the figures 

 on the plates refer. These specimens are marked A-F. A, B, and C are small 

 specimens with discs 27-31 mm. in diameter. D, E, and F are large specimens. 

 D had a disc 60 mm. in diameter. E was probably still larger, but is too frag- 

 mentary for exact measurement. F is a detached stalk which appears to have 

 belonged to a specimen with a disc also about 60 mm. in diameter. 



Shape and size. In the smallest nearly complete specimen, the disc-shaped 

 body is oval in outline, 19 mm. long, 16 mm. broad, and 2.5 mm. thick in the 

 middle. Towards the margin it thins out. The central part pf the upper, gas- 

 tral face is flat, its marginal part shghtly convex. The stalk is eccentric, obhque, 

 2 mm thick close to its point of insertion to the sponge-body (disc), and atten- 

 uated below. In seven of the nearly complete specimens the disc is fairly flat, 

 circular to oval in outline, 24-35 mm. in maximum diameter, and 5-7 mm. thick 

 in the middle. One of these small specimens is represented on Plate 9, fig. 30. 

 In these specimens the central part of the upper, gastral face is flat, slightly 

 concave or slightly convex, the marginal part usually distinctly convex. The 

 proximal end of the stalk is 2-5 mm. thick. The eccentricity of its point of 

 insertion varies considerably and is in one of the specimens so great that its 

 distance from the farthest point of the margin is thrice that of its distance from 

 the nearest. In one small specimen (Plate 9, fig. 29) the disc is a little over 

 30 mm. in diameter, 7 mm. thick in the middle, and folded in above. The upper, 

 gastral face is, apart from the remarkable infolding, nearly flat in the middle 

 and strongly convex towards the margin. The lower, dermal face is convex in 

 the middle and flat near the margin. The margin itself is very clearly defined 

 and sharp (Plate 8, figs. 28b, 29b). The stalk is, close to its point of insertion, 

 4.5 mm. thick; 8 mm. lower, where it is broken off, it is only 2.2 mm. thick. 



