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



The upper lotus is trapeziform, and has the four margins nearly straight. The 

 scutal margin is the longest, the carina! margin the shortest of the four, the tergal and 

 basal margins are almost of equal length. 



The rust ml lotus is almost triangular, the lateral margin being almost the prolongation 

 of the short basal margin. The umbo is at the extremity of the oecludent margin of the 

 scutum. Tlic valve is indistinctly divided into two parts, by a ridge running from the 

 umbo to the point where the lateral and basal margins meet. 



The infra-median lotus is triangular and rather narrow, and has the umbo at the 

 superior extremity. This superior extremity does not reach the scutal-basal angle of the 

 upper latus. 



The corinal lotus is large and almost trapeziform. The lateral and upper 

 margins are almost of the same length, and the basal margin is only a little shorter. The 

 carinal margin, on the contrary, is a great deal longer. It has the umbo at one-fourth of 

 the total length from the inferior extremity. The part above the umbo is slightly 

 excavated. 



Length of the capitulum, 13 "5 mm. 



The peduncle is extremely short (3 - 5 mm.), conical, furnished with a membrane which 

 covers the scales also. Hence these are only imperfectly visible. They form seven 

 longitudinal rows, each of them composed of about eight rather large scales. 



I have not studied the animal contained within the capitulum of this species, and 

 complemental males were not present at the place they ordinarily occupy. 



This species was taken at a small distance from Yeddo, at Station 237, June 17, 1875 : 

 lat. 34° 37' N., long. 140° 32' E.; depth, 1875 fathoms; bottom temperature, 1°7 C; 

 bottom, mud. 



Observations. — This species is nearly related to Scalpellum truncatum, Scalpellwm 

 australicum, &c. The form and structure, of the valves, however, show its distinctness. 



Scalpellum 'planum, n. sp. (PI. IV. figs. 12, 13). 



Surface of the capitulum smooth, covered by a very thin membrane. Valves thirteen. 

 Scutum triangular. Carina simply bowed, with a flat roof and the umbo at the apex. 

 Upper latus large, with the umbo near the middle of the scutal margin. Infra-median 

 latus narrow, elongate. 



This elegant little deep-sea species is represented by a single specimen. 



The capitulum is elongated and very flat. Its greatest breadth is about in the 

 middle, towards the peduncle it is a great deal narrower. The margins of the valves 

 are very distinct. The carina is separated from the tergum by an interspace filled with 

 chitinous membrane. 



