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



The shape of the body is irregularly pyriform ; it is not compressed laterally. The 

 anterior end is narrow, and tapers into the upper end of the peduncle. The posterior 

 end, on the contrary, is broad and bluntly rounded. The dorsal and ventral edges are 

 irregular ; they are, roughly speaking, parallel in their posterior two-thirds, and converge 

 rapidly in their anterior third. The sides are equally convex, the body in transverse 

 section being nearly circular. 



The peduncle is of moderate length, thin but wiry, stiff but flexible, slightly undulating, 

 though straight in its general course. It is a prolongation of the anterior end of the 

 body, but at the point of junction turns dorsally at a right angle, so as to cross the 

 branchial aperture ; it is slightly enlarged at the upper and lower extremities, and else- 

 where it is of uniform thickness. 



The branchial aperture is placed close to the anterior extremity on its dorsal edge, 

 consequently it is just under the peduncle (PL VIIL fig. 1). It is sessile but con- 

 spicuous, rather large and open, and triangular in shape — the base being anterior and the 

 apex posterior. It is surrounded by a broad fringe of close-set minute papillse or 

 processes of the test, and is directed anteriorly and dorsally. The atrial aperture is distant 

 from the branchial, being placed on the broad posterior extremity, a little to the dorsal side 

 of the middle, and directed posteriorly. Like the branchial aperture it is sessile and large. 

 It is bilabiate, in the form of a wide transverse slit, and is bordered by minute papilli- 

 form processes of the test. 



The surface, which is rather irregular, being thrown into creases here and there, 

 especially towards the posterior end, is finely granulated all over, while larger projec- 

 tions form thickened borders to the apertures, and are especially developed along a line 

 encircling the body towards the posterior extremity. This line runs in an irregular 

 undulating course round the posterior end, and thus surrounds the atrial aperture (PI. 

 VIIL fig. 1). It reaches the posterior end of the ventral edge, but dorsally it extends 

 more anteriorly, so as to cut the dorsal edge about two-fifths of the way from the 

 atrial to the branchial aperture. Where it crosses the ventral edge it is enlarged into a 

 thickened mass of triangular shape, having the apex directed anteriorly ; while in the 

 dorsal region the belt narrows considerably, and the papilla? are of smaller size. The 

 surface of the peduncle is nearly smooth, slightly ridged longitudinally in parts. 



The colour of the body is a dull brown with a slate-grey tinge where the surface is 

 least rough. The peduncle is of a pale slate-grey throughout. 



The dimensions in the two specimens are as follows : — 



