REPORT ON THE ECHINOIDEA. 109 



rest of the plate being filled with granules, miliaries, and secondaries, u-regularly 

 arranged. In the amhulacral area the pits are only slightly smaller, but there is 

 only a single large pit at the median end of the suture, the pit at the other extremity 

 of the suture is reduced to a minute impression at the angle of the coronal plate 

 adjoining the poriferous zone. There is a distinct vertical row of primaiy tubercles 

 on the outer edge of the coronal plates, extending along the whole length of the 

 poriferous zone, the rest of the ambulacral plate is occupied by an inner somewhat 

 smaller tubercle, and an irregular horizontal line of secondaries with miliaries extending 

 above the larger tubercle. The pores form very indistinct irregular vertical arcs of three 

 pairs ; the pores are separated by slight ridges, and the miliaries of the coronal plates 

 sometimes encroach on the outer edge of the poriferous zone. 



In alcohol the test is greenish, the tubercles standing out in greyish-white ; the spines 

 are short, slender, resembling those of Salmacis ; they are yellowish, with three to four 

 reddish-orange transverse bands more or less distinct. 



Galapagos is mentioned as the habitat of this species in the Eevision of the Echini; 

 this is evidently a mistake, as thus far no species of Temnopleuridaj have been recorded 

 from that locality. The specimens collected by the Challenger show conclusively that 

 this genus has the same geographical range as the other members of the family. 



'station 186. September 8, 1874. Lat. 10° 30' S., long. 142° 18' K; 8 fathoms; 

 coral sand. 



Kobi, Japan; 8 to 50 fathoms. May 17, 1875. 



"' Prionechinus. 



Pi-kmecMniis, A. Agassiz, 1879, Proc. Am. Acad., vol xiv. p. 202. 



The structure of the apical system of this genus is closely allied to that of the 

 Salmacidse. It resembles more, perhaps, that of the genus Coi:>t02ihyma of Peron and 

 Gauthier, figured on plate xv. fig. 1 1, ]6chin. foss. d'Algerie, Cotteau, Peron et Gauthicr ; but 

 as in Cottaldia, there is Isut a single row of plates of pores of equal size in the ambulacral 

 zone. The actinostome is somewhat indented, and the actinal membrane is covered by 

 pktes. The spines are seiTated, somewhat flattened, differing radically in external 

 appearance from the spines of the Triplechinidae thus far known. 



'•"Prionechinus sagittiger (PI. VI." figs. 11-14; PL XL. figs. 43, 44). 



PrionecMnim sagittiger,- A. Agassiz, 1879, Proc. Am. Acad., vol. xiv. p. 202. 



Unfortunately only poorly-preserved specimens of this interesting genus were 



collected; the largest, measuring 7-5 mm. in diameter, is evidently immature, though 



the genital openings are well developed. The actinal system of this species has ten large 



' buccal plates (PI. VI.-'' fig. 12), with others irregularly arranged; it resembles that of the 



