TEMNECHINUS MACULATUS. 287 



(PL VIII. f. l), which appear fully developed, but a single circular plate 

 (PL VIII. f. 3), slightly conical, occupying nearly the whole anal system, 

 with the exception of a small crescen1>shaped anal slit, covered by four very 

 small plates. The genital plates are large pentagonal, with a deep groove, 

 in which is situated the genital opening, having on the anal edge a cluster 

 of three or four small tubercles ; the ocular plates are also pentagonal, elon- 

 gated horizontally, indented slightly. The color of the test is greenish (in 

 alcohol), often mottled with dark violet patches : the spines are of the same 

 greenish tinge, banded irregularly with reddish transverse bands. In other 

 specimens we have the same pattern of coloration, in different shades of 

 green, with white spots irregularly scattered over the surface, or the me- 

 dian ambulacral and interambulacral spaces are colored, the tubercles rising 

 prominently from this deeper background ; the anal edge of the genital 

 plates is similarly colored. On PL VIII. f. 30, is given a part of the test of 

 Temnechinus globosus of Forbes, from a specimen considerably larger than 

 the specimen of T. maculatus (PL VIII. f. l), when the pits, which exist at 

 the base of the tubercles (PL VIII. f. 4), are just commencing above, while 

 they are well developed in the part of the test of the fossil species represent- 

 ed, but coincide in the structure of the upper part of the test with the living 

 specimens. The changes due to growth in the recent species of Temnechinus 

 are striking, the different stages from the perfectly smooth uniform granulation 

 of the smallest specimen collected (PL VIII. f. 17), with its immense actinos- 

 tome, through those represented in PL VIII. f. 14, to/. 11, and to/. J t , would 

 scarcely be credited to belong to the same species were it not for the complete 

 series collected. The different habitus of the oldest and smallest specimen col- 

 lected is best seen by contrasting (PL VIII. f. 1G and PL VIII. f. l) the two 

 extreme sizes of this species collected by Mr. Pourtales. In the youngest stage 

 (PL VIII. f. 16), the spines are slightly flattened, pointed, swollen in centre, 

 serrated, longitudinally striated ; they equal in length the diameter of the 

 test, are few in number, and remarkably large, here and there some smaller 

 spines having the same structure as the larger, and a few club-shaped embry- 

 onic spines, not yet articulated. The test is flat, pentagonal, is not separated 

 into plates, has no abactinal system proper yet specialized, beyond the single 

 large plate of the anal system and the large genital openings, in the limestone 

 network. In a somewhat older stage the spines cover the test more close- 

 ly concealing the anal plate, they have lost their fusiform shape and take 

 the form of spines figured in PL VIII. f. IS, still retaining sufficiently the 



