PODOCIDAEIS SCULPTA. 271 



by Miiller and myself.* The abactinal system, placed in a depression of the 

 abactinal part of the test, resembles that of Arbacia, having only four anal 

 plates (PL IV. f. 14), with large genital and ocular plates, which, however, are 

 not bare as in that genus, but carry small, rudimentary, knob-shaped spines. 

 The genital openings are near the anal system. The buccal membrane carries 

 ten large quadrangular plates, with rounded edges placed near the test, the 

 whole space between them and the mouth being covered by small plates 

 (PL IV. f. 9); the rest of the membrane is bare. The actinal opening is large, 

 the cuts slight, and the pores are not arranged in arcs near the mouth, as in 

 Echinocidaris. The spines are sharp, flat, spindle-shaped (PL IV. f. s) with 

 a prominent ridge running along the middle of the upper surface ; the sec- 

 tion is triangular, the longest side being the under side, which is convex, the 

 shorter upper sides being concave, as is shown better in the enlarged section 

 (PL IV. f. 15). The spines are finely granulated longitudinally, with a slightly 

 serrated edge. The large spines, as well as the knobs of the rudimentary 

 spines, are sometimes beautifully colored by dark violet pigment cells, follow- 

 ing the arrangement of the granulation. The pedicellarise have the same 

 coloration. The tentacles, to judge from alcoholic specimens, must have 

 been very large, though not possessed of a powerful disk ; being, especially 

 near abactinal pole, blunt, or more or less pointed (PL IV. f. 8), as in 

 Arbaciadae ; the test, when prepared to show the structure, was of a deli- 

 cate cream-color, upon which the brilliant coloration of the knob-shaped 

 spines stood out in bold relief. 



138 to 315 fathoms. 



* This genus may be truly said to represent Temnopleurus among the Arbaciadae. It is closely 

 allied to Glypticus, where the primary tubercles are gradually changed to irregularly shaped ridges, cover- 

 ing the abactinal part of the test. For figures of Glypticus see Goldfuss, Pet. Germania; ; and Agassiz, 

 fichinod. foss. Suisses. 



