POROCIDARIS COBOSI. 31 



secondaries ; these with the scrobicuhir area occupy nearly the whole of 

 each interambulacral plate ; along the median interambulacral line, some 

 of the larger scrobiciilar areas below the equatorial belt are flanked by 

 half-circles of secondaries and irregular rows of minute miliaries. On 

 the interambulacral plates below the equatorial belt, the mammary boss is 

 high, the tubercles are small and perforate. On both sides of the sharply 

 cut median line of suture of the ambulacral plates runs a vertical line of 

 secondaries with an inner row of irregularly placed miliaries. Unfortunately 

 the actinal system is wanting; it is pentagonal and 10 mm. in greatest 

 width. 



The primary radioles (PI. 12, fig. 19) are slender, gradually tapering, 

 with lines of blunt serrations. The shorter primary radioles are slightly 

 flattened at the extremity and indistinctly fluted. The longest equatorial 

 radiole is 37 mm. in length. Others of the shorter radioles taper rapidly 

 to a point above the equatorial belt. The secondary and miliary spines are 

 slender and pointed ; a few of the secondaries round the scrobicular areas 

 are stouter at the base. The larger interambulacral spines round the scro- 

 bicular areas on the equatorial and actinal side are narrow and flattened, 

 with rounded tips. The ambulacral spines are blunt, somewhat cylindrical 

 or flattened. Only a single kind of pedicellaria is found, as the tridentate 

 and large globiferous are both wanting. The small globiferous ones are 

 very numerous everywhere and very variable in size and form. The valves 

 are elongated and rather slender, and the lip and end-tooth may both be 

 present, or either or both be wanting. In length they range from .28 to 

 .91 mm., while the opening varies in size from .15 to .32 of the length. 

 The stalk is shorter than the valves, or as long, or even twice as long. 



Station 3709. Off Spithead, Shimizu Harbor, Honshu Island, Japan. 

 173-260 fathoms. Sft. bl. vol. m. r. 



PoEOCiDARis Desor. 

 Porocidaris Cobosi A. Ag. 



Porocidaris Cobosi A. Ag. 1898. Bull. M. C. Z., XXXII, 5, p. 74. PI. Ill, figs. 2-5. 



Plate 7. 



Only tridentate pedicellariae are present in this beautiful species, even 

 the small globiferous pedicellariae being entirely wanting. 



