REPORT ON THE RADIOLARIA. 1725 



The genus Conchopsis and the following Conchoceras differ from the other 

 Concharida in the strong lateral compression of the shell, so that each valve is provided 

 in the sagittal plane with a sharp prominent keel, comparable to the dorsal and the anal 

 fin of fishes. These compressed shells are in general twice to three times as large 

 as the more roundish and keelless shells of the five preceding genera. The sculpture 

 of the fenestrated valves is extremely elegant. Conchopsis possesses at the aboral 

 hinge not the two prominent caudal horns, which mark the following genus Concho- 

 ceras, but in some species a peculiar ligament connects the aboral ends of both valves. 



1. Conchopsis orbicularis, n. sp. (PI, 125, fig. 3). 



Shell subcircular, lenticular, strongly compressed on both sides, nearly as high as long, its 

 sagittal perimeter nearly circular ; frontal and cinctural perimeter spindle-shaped. Borders of the 

 two boat-shaped valves smooth in 0'4 of the oral part, and in 01 of the aboral part of their length, 

 strongly dentated in the remaining O5 middle part ; about twenty-five slender, straight teeth on 

 each side of one valve, size of the teeth increasing from the aboral towards the oral pole. In the 

 half lateral perimeter of the shell (along the right and the left borders of each valve) sixty to sixty- 

 five pores, in the half sagittal perimeter (along the keel of each valve) eighty to eighty-five pores, 

 in the half equator sixty to sixty-five pores. 



Dimensions. Length of the shell 0'53, height 0'55, breadth about - 2. 



Habitat. South Atlantic, west of Tristan da Cunha, Station 333, depth 2025 fathoms. 



2. Conchopsis compressa, n. sp. (PI. 125, figs. 7, 8). 



Shell lenticular, strongly compressed on both sides ; proportion of its longitudinal diameter to 

 the sagittal and lateral = 10 :9 : 3, its sagittal perimeter elliptical (fig. 7), cinctural and frontal 

 perimeter spindle-shaped (fig. 8). Borders of the two boat-shaped valves smooth in 0'3 of the oral, 

 and 0'3 in the aboral part, dentated in the remaining 0'4 middle part ; about forty to forty-four very 

 slender teeth of equal size on one lateral edge of each valve. In the half frontal perimeter of the 

 shell (along the border of the valve) sixty-four to sixty-eight pores, in the half sagittal perimeter 

 (along one valve-keel) seventy to eighty pores, in the half equator forty-four to forty-eight pores. 

 Ventral and dorsal pores linear, three to four times as long as the circular, lateral pores. 



Dimensions. Length of the shell 0'6 to 0'8, height 0'55 to 0'72, breadth 0'2 to 0'3. 



Habitat. North Pacific, between 30 and 40 north latitude (between Japan and San Francisco), 

 in depths from 2000 to 3000 fathoms frequent, Stations 241 to 252. 



3. Conchopsis carinata, n. sp. (PL 123, fig. 8). 



Shell subcircular, lenticular, in the central half slightly compressed, nearly spherical, in the 

 peripheral half strongly compressed, with a broad, hyaline, smooth keel on the sagittal plane. 

 Borders of the two valves smooth in the 0'2 of the oral, and O'l of the aboral part, strongly 



