118 THE VOYAGE OF H.M.S. CHALLENGER. 



the body is somewhat compressed laterally. The anterior extremity is very narrow and 

 attenuated, being more produced, and tapering more gradually than in any of the other 

 species. The posterior end is broad and slightly rounded, having a truncated appearance. 

 It forms a nearly straight line dorso-ventrally, and curves round sharply at the ends to 

 become continuous with the dorsal and ventral edges. These two edges are almost 

 equally curved. They diverge from the narrow anterior end for about half the length of 

 the body, at which point the greatest breadth (dorso-ventral) is attained. They then run 

 parallel for a short distance, and finally curve sharply and evenly into the ends of the 

 posterior extremity. The two sides are equally, but slightly convex. 



The peduncle is rather long and thin, but stiff (PI. X. fig. 7). It is attached to 

 the attenuated anterior end of the body, and forms a continuous line with the dorsal 

 and ventral edges. It may be traced for a short distance along the ventral edge, partly 

 imbedded in the test. After leaving the test it runs for a short distance anteriorly, and 

 then curves round dorsally at nearly a right angle, and preserves a slightly undulated 

 course down to the base of attachment. At this point it is slightly expanded, elsewhere 

 it is of the same thickness throughout. 



The branchial aperture (PI. X. fig. 7) is situated on the dorsal edge of the anterior 

 end, and is nearly one-fourth of the length of the body, from the point of attachment of 

 the peduncle. It is conspicuous but not prominent. It has the form of a transversely 

 elongated rather crescentic slit, having the concavity directed posteriorly (PL X. fig. 8), 

 and its anterior edge forming an angle in the middle so as to give the aperture a sub- 

 triangular form like that of Culeolus recumbens. The anterior and posterior lips are 

 not prominent and are scarcely marked. The opening is directed dorsally and anteriorly. 



The atrial aperture lies in the centre of the large posterior end, and looks directly 

 posteriorly (PI. X. fig. 7). It is sessile but conspicuous, and is a large transverse, slightly 

 crescentic, slit, gaping slightly, and having no raised lips (PI. X. fig. 9). The edges are 

 dorsal and ventral. 



The surface is even but very rough, being covered all over with conical and dome- 

 shaped papillae (PL X. figs. 7, 8 and 9). These papillae are larger than those scattered 

 over the test in any of the other species, but here they are not modified in any particular 

 region to form a band round the atrial aperture as in Culeolus murrayi, Culeolus recum- 

 bens, and Culeolus <perlatus. The surface of the peduncle is slightly roughened like that 

 of the last species. 



The colour of the body is a pale yellowish-grey — the papillae having a decided yellow 

 tinge. The peduncle is darker, being of a greyish- brown colour. 



The dimensions are as follows : — 



