290 TEIGONOCIDARIS ALBIDA. 



irregular (PI. IV. f. S), extending from the base of the different tubercles, 

 both primary and secondary, and uniting them all in a complicated, raised 

 system of network, with irregularly shaped cells, the ridges leaving more or 

 less deep pits, giving the test the appearance of having been gouged out in 

 spdls ( PI. IV. f. l). The spines arc long, slender, somewhat transparent, 

 longitudinally striated, with slight transverse striatum (Pi. IV. f. 4). The 

 abactinaJ system resembles that ol Ilemipedina. but the anal system is cov- 

 ered by only four triangular plates, one of which is much larger than the 

 others 1 PI I V. /'. /). From the fact that in the youngest specimens exam- 

 ined we find them already, 1 am tempted to suppose they never increase in 

 number, and remain as they are, as in Arbacia. The actinal membrane is, as 

 in some specie's of Toxopneustes, entirely covered by a number of rather 

 large plates irregularly arranged, the ten buccal plates being hut slightly 

 more prominent (PI. IV. f. .') thru the others. The actinal opening is of 

 moderate size, slightly indented ; the auricles are exceedingly slender, and 

 disconnected at the extremity. There are hut two principal rows of primary 

 tubercles, both in the ambulacra] and Lnterambulacral zone, with hut five to 

 six minute tubercles seated upon the connecting ridges in the latter zone, 

 and two or three upon each plate in the former. The poriferous zone is 

 narrow ; the pores are placed obliquely in an unbroken vertical zone, three 

 to each ambulacral plate, and separated by ridges running from the ambula- 

 cra] tubercles to the interambulacral zone, similar to those joining the tuber- 

 cles. The test, as well as the spines, are almost white, the latter having only 

 a slight tinge of yellow when largest. The whole test is covered with pedi- 

 cellariae ( PI. IV. f. 5), having a large pointed head articulated upon a long, 

 comparatively slender peduncle, seeming scarcely capable of supporting the 

 bulky head. 



In younger specimens | PI IV. f. (]), the reticulations connecting the 

 smaller number of larger tubercles are broader, the pits less numerous and 

 not so deeply cut (PI. IV. f. 7); the secondaries, however, show no regular 

 arrangement, the spines are comparatively longer, the arrangement of the 

 poriferous zone is the same, and the ahactinal system does not vary materi- 

 ally from the older specimens figured. The only approach we have to a 

 similar reticulation in any other genus is in Echinocyphus, but then it is 

 limited to a few spurs radiating from the primary tubercles like spokes. 



From 40 to 270 fathoms. 



