02 TIIE VOYAGE OF H.M.S. CHALLENGER. 



The rostral lotus is very low, quadrangular, the scuta! margin nearly parallel to the 

 basal margin. 



The infra-median latus is small, triangular, and has the umbo at the apex. 



The carinal latus is larger than the other latera of the lower whorl. Its carinal 

 margin is arched, its upper margin hollowed out. Where the two margins meet, the umbo 

 is situated ; it is distinctly curved to the front. The lateral and basal margins are 

 almost of the same length. 



Length of the capitulum, about 5 mm. 



Tin' peduncle is about one-third the length of the capitulum, cylindrical; furnished 

 with four longitudinal rows of very prominent scales, each row containing about five of 

 these scales. 



This species was taken at Station 204, November 2, 1874 ; lat. 12° 43' N., long. 122° 

 10' E.; depth, 100 fathoms and 115 fathoms; bottom, mud (near Luzon). 



Observations. — The circumstance that only a single specimen of this species has been 

 obtained makes it impossible to enter into details as to the structure of its mouth, cirri, 

 kc. A complemental male was not present. 



Scalpellum truncation, n. sp. (PL V. fig. 13). 



Surface of the valves naked, with very prominent ridges ; valves fourteen, closely 

 locked together. Carina simply and feebly bowed, with the umbo at the apex, and with 

 the roof flat, much increasing in width from the upper to the lower extremity, bordered 

 on each side by a very prominent ridge. Rostrum hardly visible. Tergum truncated. 

 Upper latus trapeziform. 



This species is represented by a single specimen. Its shape is a very characteristic one, 

 on account of the truncated form of the tergum, the occludent margin of which describes 

 an angle with the occludent margin of the scutum. 



Capitulum very flat, consisting of fourteen valves. Valves entirely naked, with very 

 distinct ridges and furrows over the surface ; capitulum not very elongate, and having its 

 greatest breadth about the scutal angle of the tergum. 



Scutum with the umbo at the apex, which projects over the tergum; occludent margin 

 almost entirely straight ; basal margin short, at a right angle with the occludent margin ; 

 lateral margin convex ; tergal margin slightly hollowed out. Valve divided into two 

 triangular parts by a rather prominent ridge, which runs from the apex to the 

 basal-lateral angle. 



Tergum triangular ; the occludent and scutal margins describe an angle of 90°. The 

 scutal margin slightly undulating, the true scutal part being convex, the other hollowed 

 out The carinal margin is arched. The umbo is at the apex, where the occludent and 

 carinal margins describe a rather obtuse angle. 



