G6 THE VOYAGE OF H.M.S. CHALLENGER. 



The \'isceral mass is globular, and of au opaque, yellowish-white colour. It lies at 

 the base of the atrial siphon, rather to the right side of the posterior end of the 

 endostyle (PL VI. figs. 1 and 3, vise). 



Salpa echinata, n. sp. (PI. V. figs. 1-10). 



External Appearance. — The body is elongated, sub-cylindrical, and rather swollen 

 towards the posterior part. The anterior end is narrow, but rounded. The posterior 

 end is wider, but more irregular in shape. The dorsal surface is flat ; the ventral is 

 gently convex. The branchial aperture is on the dorsal surface near the anterior end. 

 It is rather small, and is semicircular in outline. The atrial aperture is placed at the 

 posterior end of the body, and is surrounded by irregular spinose processes of the test. 

 The surface is smooth, with the exception of a series of dorsal, lateral, and ventral 

 echinated ridges, which run more or less longitudinally from end to end. These ridges 

 become more numerous anteriorly, but more prominent towards the posterior end of 

 the body. 



Length, 4 cm. ; breadth, near anterior end, 7 mm., near posterior end, 1 cm. 



Tlie Test is clear and transparent. It is soft and rather thin, except where thickened 

 to form the echinated ridges, and on the posterior part of the ventral surface, over the 

 visceral mass. The posterior swollen part where the ridges are largest is considerably 

 stiffer than the anterior part. 



The Mantle has the musculature moderately developed. There are nine transverse 

 muscle bands visible on the sides of the body. Of these, the first, second, and third 

 approach one another dorsally, and fuse in the middle line, while the remaining six 

 keep distinct, and are nearly equidistant from one another. All the muscle bands 

 die away ventrally. 



TJie Endostyle is very distinct. It extends forwards in front of the branchial aperture. 



TJie Dorsal Tuhercle is simple, but of fairly large size. It is elongated antero- 

 posteriorly, and has gently rounded ends. 



Tlie Visceral Mass is placed near the posterior end of the ventral surface. It is 

 not large. 



Localities. — (1.) October 21, 1875; Station 288, South Pacific; surface; lat. 40° 

 3' 0" S., long. 132° 58' 0" W. ; surf. temp. 54°-5 ; two specimens. 



(2.) November 5, 1875; Station 295, South Pacific; surface, taken at night; lat. 

 38° 7' 0" S., long. 94° 4' 0" W. ; surf. temp. 58°-5 ; one specimen. 



(3.) January 21, 1876 ; Station 314, near the Straits of Magellan ; lat. 51° 35' 0" S., 

 long. 65° 39' 0" W. ; depth, 70 fms. ; bottom temp. 46°, surf temp. 48° ; two specimens. 



(4.) April 12, 1876 ; Station 351, Atlantic, off the West Coast of Africa; surface; 

 lat. 9° 9' 0" N., long. 16° 41' 0" W. ; surf. temp. 81°-8 ; one specimen. 



