1708 THE VOYAGE OF H.M.S. CHALLENGER. 



the middle third of the shell, diverge upwards, and are slightly arcuate, covered with numerous 

 curved spines. Their base is pierced by four pedal pores. The peristome is a narrow sagittal 

 fissure, placed in the radius of the odd or dorsal foot, and bears two opposite teeth on its two 

 corners. The teeth are cylindrical, longer than the shell, covered with curved spines, and ascend 

 in a parallel and vertical manner ; each is perforated at the base by three large dental pores. 



Dimensions. — Length of the shell 1'4, breadth 1'2. 



Habitat. — North Pacific, Stations 244 to 250, depth 2050 to 3050 fathoms. 



6. Tuscarora porcellana, John Murray (PL 100, figs. 6o, Qb). 



Tuscarora porcellana, Jolin Murray, 1879, in litteris, Narr. ChaU. Exp., pL A, fig. 18. 



Shell pear-shaped, with three lateral perradial feet in the lower half of the shell, and two 

 parallel vertical teeth on the mouth. The three lateral feet arise between the middle and the 

 lower third of the shell, are straight, cylindrical, spinulate, about as long as the shell and diverge 

 downwards ; their base is pierced by four ovate pedal pores. The two parallel and vertical teeth 

 are straight, shorter than half the shell, and opposite in the sagittal plane, on the two corners of the 

 narrow mouth, in the radius of the dorsal odd foot. The base of each tooth exhibits four cordate 

 dental pores. 



Dimensions. — Length of the shell 1'5, breadth 1"3. 



Hahitat. — South Atlantic, Station 325, depth 2650 fathoms. 



Subgenus 3. Tuscarilla, Haeckel. 



Definition. — Shell with three perradial equidistant feet, and with four crossed 

 equidistant teeth around the mouth. 



7. Tuscarora belknapii, John Murray. 



Tmcarora helhiapii, John Murray, 1879, in litteris, Narr. ChalL Exp., vol. i. p. 226, pi. A, 

 fig.s. 15, \ba-\M. 



Shell pear-shaped, with three lateral perradial feet in the upper third, and four crossed teeth 

 around the mouth. The three arcuate feet are thin, cylindrical, covered with small curved thorns, 

 and arise at the base of the peristome, between the upper and middle third of the shell ; they ascend 

 diverging to the height of the mouth, and are then curved downwards in a large arc, twice to three 

 times as long as the shell. The base of each foot is dilated and pierced by three pedal pores. The 

 four thin and long teeth of the peristome are similar to the feet, ascend in a slightly diverging 

 manner, and are so placed that two opposite lie in the sagittal plane (or in the radius of the dorsal 

 odd foot), whUst the two others are opposite in the frontal plane (perpendicular to the former). 

 The base of each tooth exhibits two large ovate dental pores. 



Dimensions. — Length of the shell 2-5, breadth 1-5. 



Habitat. — South Pacific, Station 293, depth 2025 fathoms. 



