GONIOPNEUSTES PENTAGONUS. 337 



are rarely more than two well-developed secondary tubercles on each ambulacral 

 plate, but there are quite a number of very small ones, in addition, in the porif- 

 erous area. The arcs of pores are very oblique and are not at all crowded. The 

 pits at the angles of the plates are fairly distinct but are exceedingly small in 

 both ambulacral and interambulacral areas. 



The periproct is covered by about 30 small plates, no one of which is notice- 

 ably larger than the others. Oculars I and V are broadly insert but the others 

 are completely shut out. The ocular pores are large and placed near the centre 

 of the plate, but curiously enough no genital pores are to be seen, even with a 

 lens. Each genital plate carries a single secondary tubercle and smaller ones 

 are to be found on oculars I, III and IV. There are also rather numerous 

 miliary tubercles on oculars, genitals, and periproctal plates. The buccal 

 membrane is rather thick, thicker at least than in Amblypneustes, and, sur- 

 prising to find, carries numerous small, scattered plates which are rather crowded 

 around the mouth. The buccal plates themselves are rather large and carry 

 large tube-feet; the two of each pair are near together but the pairs are well 

 separated from each other. The buccal plates and the scattered plates distal 

 to them carry pedicellarise. The gill-cuts are deeper and more conspicuous than 

 in Amblypneustes. 



The primary spines are about 6 mm. long, in the mid-zone; they are very 

 finely striated and taper to a blunt point. The secondaries are shorter and more 

 slender and many appear to be pointed, though some are slightly swollen near 

 the tip. Pedicellarise are very common, but no tridentate could be found. The 

 others remind one at once of Gymnechinus. The globiferous have valves (PI. 93, 

 fig. 19) about .30 mm. in length, with a long end tooth (PI. 93, fig. 20) but no 

 lateral teeth. The ophicephalous are larger, having valves (PI. 93, fig. 18) about 

 .40 mm. long, but they show no distinctive characteristics. The triphyllous 

 are very smalt, having valves (PL 93, fig. 21) only .12 mm. long. The calcareous 

 spicules in the tube-feet are C-shaped. Sphseridia are few and very small. 

 The test is almost fawn-color but has a distinct purplish cast, except in the 

 bare median areas of both ambulacra and interambulacra. The primary spines 

 are pure white but the secondaries are gray, tinged with purple. The buccal 

 membrane is dark, but the plates it bears are light. 



