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



is regularly marked and rather narrow (PI. XXVIIL* figs. 3, 4). The primary spines are 

 only slightly curved and flaring, generally uniform in width on the sides, but below flaring 

 and club-shaped. There are four well-marked genital pores (PL XXVIII." fig. 12) situated 

 in the trivium, which is well separated from the bivium. The genital organs are short 

 clusters (PL XXVIII." fig. 13) of from seven to eight large purse-like pouches, which do 

 not apparently ramify like the ovaries of Pourtalesia lagimcula. The madreporic body 

 is insignificant. 



This species, while having the outline of Pourtalesia miranda, P. laguncula, and P. 

 jeffreysi, has the stout test and close tuberculation of Pourtalesia ceratopyga. The actinal 

 groove is comparatively smaller, shallower, and narrower than in those species, and the 

 slight re-entering angle formed hj the anterior extremity when seen from above, and 

 the more sloping anterior extremity form a passage between the bottle-shaped forms 

 like Pourtalesia miranda, and the triangular types with posterior apex like Pourtalesia 

 cerat02)yga. 



The actinal and abactinal lines of the snout are nearly parallel, forming a sharp angle 

 at the abactinal extremity. The anal groove is short and deeply indented. Judging from 

 the size of some of the fragments of the test of this species, it must have attained a length 

 to from 90 to 100 mm. 



The colour of the test in alcoholic specimens is of a light claret, the whitish-pink spines 

 standing out in relief upon the dark background. The colour of the test is often darker 

 on the abactinal keel and on the anterior median interambulacral ridges of the abactinal 

 side of the test. 



Station 147. December 30, 1873. Lat. 46° 16' S., long. 48° 27' E. ; 1600 fathoms ; 

 bottom tempei'ature, 0"8° C. ; globigerina ooze. 



Station 157. March, 3, 1874. Lat. 53° 55' S., long. 108° 35' E. ; 1950 fathoms; 

 diatom ooze. 



Station 298. November 17, 1875. Lat. 34° 7' S., long. 73° 56' W. ; 2225 fathoms; 

 bottom temperature, 1 "3° C. ; grey mud. 



*Pourtalesia ceratopyga (Pis. XXVIII. XXXV." fig. 17 ; PL XLI. figs. 44-46 ; 

 PL XLIL figs. 17-23; PL XLIIL figs. 15-17; PL XLV. figs. 53-59). 



Pourtalesia ceratopyga, A. Agassiz, 1879, Proc. Am. Acad., vol. xiv. p. 205. 



Nearly complete specimens of a large Poiw'ia^esm which were brought up from 2225 

 fathoms at Station 298, form, with Pourtalesia rosea, an entirely distinct group from the 

 other species collected. This species is remarkable for the great breadth (PL XXVIII. 

 fig. 1) of the anterior extremity, with the re-entering median ambulacral region extending 

 laterally so as to form a rounded angle with the sides; this part of the test is by far the 

 widest, and it slopes very rapidly towards the posterior extremity. The width of the anal 

 snout is proportionally smaller than in the other species of the group ; the sunken actinal 



