Nlj THE VdVAUE OF JE.M.S. CHALLENGER. 



broad chitinous interspaces, which give the animal a very characteristic appearance. 

 The capitulum consists of fourteen valves; there is a distinct rostrum, but no sub- 

 carina. 



The scutum is elongate, very narrow, especially towards its upper extremity, hence 

 almost triangular. The occludent margin is straight, the lateral margin also; the latter 

 passes with a very obtuse angle into the short tergal margin. The basal margin is short. 

 The umbo is at the apex, which projects considerably over the tergum. 



The tergum is triangular, not very large, rather slender, obtusely pointed at the under 

 extremity. 



The carina is well developed, simply bowed, with the umbo at the apex. The apex 

 reaches as far as half the length of the carinal margin of the tergum. The carina has no 

 flat roof, being distinctly carinated ; laterally it is regularly bowed, so as to show a 

 semicircular line on section. 



The upper latus is quadrangular and elongate. Its scutal margin is hollowed out, 

 its tergal margin is short and straight ; its carina! margin is straight also. The under- 

 most part of the valve, which penetrates between the infra-median and the carinal latera, 

 is a great deal narrower than the upper part. 



The rostrum is relatively large, and has an oval shape. It is covered on either side 

 by the free edges of the rostral latera, which touch each other in a single point beneath 

 the occludent margins of the two scuta. 



The rostral latus is quadrangular, with the rostral margin arched, and the scutal 

 margin straight and a' great deal longer than the ba3al margin; the lateral margin is 

 large and slightly hollowed out. 



The infra-median latus is elongate, triangular, with the umbo at the apex. The 

 valve is distinctly protuberant beyond the surface of the two adjoining latera. 



The carinal latus is relatively large, and has the umbo at the apex. Its carinal 

 margin is distinctly arched, its upper margin hollowed out. The lateral margin is straight, 

 and so is the basal margin. A Aery prominent ridge divides the valve into two triangular 

 parts. The apex is considerably curved to the front, so as to touch the carinal-basal 

 angle of the upper latus. 



Length of the capituluni, 13 mm. 



The 'peduncle is conical, being a great deal narrower near its attachment than near 

 the capituluni ; with the valves of the lower whorl the peduncle forms a kind of calyx for 

 the reception of the other valves. The peduncle is covered by calcareous scales placed 

 in six longitudinal rows, each containing about seventeen scales. The peduncle with its 

 rows of scales has undergone a slight torsion. 



Of this species I have not studied the structure of the animal enclosed within the 

 capituluni; nor have 1 been fortunate enough to observe a complemental male at the 

 place it ordinarily occupies. 



