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



The tergum is quadrangular, its apex is not blunt, though not very pointed. The 

 rostrum is distinctly convex, and is furnished with three furrows, which run from 

 the apex to the rostro-carinal margin; this margin shows three excavations separated 

 by teeth. The apex of the valve slightly projects beyond the scutum. The carina 

 has the apex projecting much farther, and is more slender than the rostrum; the 

 furrows on its surface are still deeper than those of the rostrum. The immovable scutum 

 consists of two triangular parts; a large one with a beaked apex, and another one much 

 narrower and forming almost a right angle with the former. A well-developed radius 

 covers a considerable part of the immovable tergum. This consists of a middle portion, 

 which is curved, narrow at the apex, and very broad at the base; a distinct oval 

 portion, which is placed between the middle portion and the immovable scutum ; and, 

 finally, a second lateral portion, which is quite on the carina! side of the shell. This 

 latter portion is very narrow at the apex, and does not increase much in width downwards. 

 It can be traced to where it reaches the carina. 



In this species the form of the immovable scutum and tergum is no doubt most 

 peculiar ; the great flatness of the main portions, together with the almost perpendicular 

 position of the lateral parts, is in none of the other species so striking. The species is 

 also remarkable for the strong development of the furrows and ridges, both on the scutum 

 and tergum and on the rostrum and carina. 



The height of the specimen is 5 "5 mm., the distance from the apex of the carina to 

 that of the rostrum is not quite 5 mm. The specimen was found attached to what I 

 think is a piece of a Polyzoon. It was taken in the Pacific Ocean; the bottle has the 

 Station number 170; according to the printed list of Stations two dredgings were 

 taken at this Station. I feel unable to decide from which of these the animal was pro- 

 cured, so I give them both. 



Station 170, July 14, 1874; kit, 29° 55' S., long. 178° 14' W.; depth, 520 fathoms; 

 bottom temperature, 6°-0 C; bottom, rocks. Lat. 29° 45' S., long. 178° 11' W.; depth, 

 630 fathoms; bottom temperature, 4° - C; bottom, rocks. 



Verrncn quacfoangularis, n. sp. (PI. XL figs. 10, 11 ; PL XII. figs. 8-12). 



Shell dirty white ; surface smooth, with not very prominent growth-ridges. Walls 

 nearly parallel to each other and perpendicular to the surface of attachment. Base 

 elongate oval. Movable scutum relatively large, with the upper articular ridge not 

 distinguishable, and with a very prominent third articular ridge. This ridge is sepa- 

 rated from the tergal margin by a narrow interspace. Movable tergum almost regularly 

 rhomboid, with a recurved and blunt apex. Apex of the carina projecting freely; that 

 of the quadrangular rostrum does not project, or only very little, Rostrum and carina 

 articulate together l>v means of two teeth on each of the two valves. 



