ECHINOIDEA. 
485 
Eciiinoidea. 
Reparation of broken spines. — Carpenter (M. Micr. J. p. 225j gives up the 
idea that the reparation of broken spines in Sea-urchins is effected by any 
investing membrane ” of the spine. The restorative power he considers to 
reside in the protoplasmic matrix filling up the interspaces of the calcareous 
network of the spine ; and the continuity of the new growth with the outer 
layer of the stump, and its apparent derivation therefrom, while it is abruptly 
marked off from the central part, he accounts for by supposing that this 
sarcodic basis substance ” may after a time cease to occupy the older and 
inner portions of the spine, and become restricted to the newer and outer. 
Fedicellarice and Ambulacra. — A very minute description of these organs in 
the Echinoidea is~given by Perrier, Ann. Sc. Nat. xii. p. 197. As regards 
the Irregidar Urchins, he had, at the time this paper was published, not de- 
tected calcareous terminal rosettes on the ambulacra of any of the genera, 
while he had found pedicellarige only in the Spatangoids. Most specimens 
of Irregular Urchins, as they occur in museums, have their external ap- 
pendages pretty well rubbed off. However, in a subsequent short paper 
(/. c, t. xiv. 1870), M. Perrier states that ho has found calcaroons rosettes on 
the ambulacra of JEchmoncus, and mentions also two different forms of pedi- 
cellarim from the same genus. 
The same author (N. Arch. Mus. v. p. 22G), after carefully examining the 
disposition of the ambulacral pores of the regular echinids, gives the follow- 
ing classification of the group, embodying also his previous researches on 
their pedicellariae and ambulacral tubes : — 
Regular or Endocyclical Urchins. 
Openings of the intestinal canal situated at the two poles of the test. 
Anus surrounded by genital and ocular plates. Ambulacra not petaloid ; 
ambulacral tubes terminated by a flattened disk, which is supported by a 
calcareous rosette of from four to six pieces serrated at their outer margins, 
and united by a calcareous framework surrounding the central orifice. 
I. — Test circular. Pedicellarise of three pieces. 
A. — Ambulacral areje narrow, each semiarea containing only a double 
line of pores, more or less flexuous. Pedicellaria-head directly fixed to a 
solid prolongation of the stem. Spicules of the ambulacral tubes spindle- 
shaped, or forming arcs of circles roughened with spines. Tubercles of the 
test crenulated and perforated. 
Genera : Cidaris, Leiocidaris^ Goniocidaris. 
B. — Ambulacral areae large ; each ambulacral plate presenting from 7 to 9 
pairs of pores disposed in a double flexuous line in the upper and middle 
regions of the test, but accumulated without order near the peristome. 
Pedicellaria of the ophiocephalous type, not directly fixed to the stem. 
Spicules of the ambulacral tubes spindle-shaped. Tubercles of the test not 
crenulated or perforated : — Echinoddariens.^' 
Genus Echinocidaris. 
0. — A mbulacral areas broad. Pores disposed in more or less oblique trans- 
verse bands of pairs. Pedicellarias not directly fixed to the stem, and be- 
longing to the tridactyle type. Spicules of the ambulacral tubes irregularly 
branclied or in the form of irregularly perforated plates, along with which 
may occur some simple arcuate spicules. Tubercles of the test crenulated 
and perforated : — Diademiens.''' 
Genera : Diadema, Savignya, Astcropyga. 
