464 
ECHINODERMATA. 
ECHINOIDEA. 
The following (somewhat abridged) systematic arrangement of the regular 
Sea-urchins is given by Troschel, SB. Ver. Rheinl. xxviii. p. 91 : — 
A. Tubercles perforated. 
a. Tubercles smooth (in living forms) ; ambulacral area without per- 
forated tubercles j interambulacral area with 2 rows of large 
perforated tubercles ; no oral notches, Cidariidce. 
h. Tubercles crenulatedj ambulacral area with perforated tubercles; 
interambulacral area with several rows of large ones ; oral notches 
distinct Diadematidcs. 
B. Tubercles not perforated. 
a. Tubercles crenulated Salmacidce. 
h. Tubercles smooth, 
a. Sutural pores Mespiliidas. 
/3. No sutural pores. 
* Periproct closed by 4 plates Echinocidariidce. 
** Many small plates on the periproct. 
t Body circular or pentagonal. 
I 3 pairs of pores on each arc. 
— Oral notches shallow, no ocular plate reaching the pori- 
proct Echinidce. 
= Oral notches deeper than broad j 2 ocular plates reaching 
the periproct TiHpneustid(s. 
II More than 3 pairs of pores on each arc. 
• Toxopneustidce. 
ft Body elliptical Echinometrid<B, 
0. K. Hoffmann (“ Zur Anatomic der Echinen und Spatangen,” Niederl. 
Arch. Zool. i. pp. 11-112, pis. 3-10) treats of the external structure and the 
reproductive and vascular systems ; and compares the structure of the Echino- 
dermata with that of the worms. A second paper is promised, on the Asternd<e 
and Ophiuridce. 
Cidaris. C. Stewart (^^ On the Minute Structure of certain Hard Parts of 
the genus Cidaris^'^ Q. J. Micr. Sci. xi. pp. 61-56, pi. 4) arrives at the following 
results : — ^The spines of the recent Cidariidce are characterized by the dense 
crust which terminates their growth ; the pedicellariae by the special chamber 
found in each jaw, and by the calcareous stem divided into 2 parts, the upper 
being in immediate contact with the head ; the ambulacral tubes by being 
surrounded by the concentrically curved spicules, which give them a ringed ap- 
pearance. These characters are common and peculiar to all recent Cidariidce. 
(The fossil species are not considered, as they do not admit of a complete and 
satisfactory examination.) The ovary, strengthened by triangular plate-like 
or radiate spicules (the former most abundant), but not retaining the form of 
its component tubules, in the dry state also affords a constant feature, pe- 
culiar to this genus. 
Echinocidaris punctulata, Desm., and Laganum decagonale^ Less., photo- 
graphed by A. Agassiz, Bull. Mus. 0. Z. 1871. 
