ECHlNIDiTI. 
443 
bathymetrical and geographical distribution. Reference is made below to 
the genera and species described in this part. (The figures on the plates are 
not cited, owing to their frequent dispersion on several plates.) 
CidarintB, 
Cidaris hysU'iVj Lam., is united with C. papillata by W. Thomson (23), 
since every possible link can be shown between them : 100-400 fath., from 
Fserd to Gibraltar, small specimens frequently down to 1000 fathoms. C. af- 
Jinis apparently distinct, though it is sometimes not easy to draw the line 
between them and small forms of papillata'^'* abundant in the Mediterra- 
nean, and locally off Portugal, The three species are united with each 
other and with Dorocidaris ahyssicola, under the name of D. papillata, by 
A. Agassiz (Rev. pp. 254—268, tab.). Cidaris trihuloides, Lamk. : Agassiz, 1 . c. 
pp. 252-254, pi. 
Porocidaris purpurata, sp. n., W. Thomson, 1. c., off the ‘‘Butt of the Lews,” 
600- GOO fath. The genus, hitherto only known in a fossil state, is chiefly 
distinguished by the paddle-like spines surrounding the mouth, and a ten- 
dency to coalescence in the scrobicidar arere. The “ row of small holes sur- 
rounding the tubercles of the primary spines in the scrobicular area,” formerly 
considered a primary character, is wanting in the recent species. 
Saleniinae. 
Salenia (Salenocidaris, olim) varispma, Agassiz, 1. c. pp. 258-262, pi. 3. 
EchinothuriiTKS. 
Named after the fossil Echinothuria, Woodw., from the chalk. Intermediate 
between the Cidarinm and Eiadeinatinoi, Test circular, flexible, much de- 
pressed; plates of the perisonm long and strap-shaped ; the iuteramhul acral 
plates overlap each other regularly from the apical towards the oral pole, 
while the ambulacral plates overlap in a similar way in the opposite direc- 
tion ; the latter are essentially within the former, which overlie them along 
their outer edge. Ambulacral pores trigeminal, in wide arcs ; the two pairs 
of pores of each nearest the centre of the ambulacral area pierce two small 
accessory plates, intercalated between the ambulacral plates, while the outer 
pair pass through the ambulacral plate itself near its outer extremity. Dorsal 
ambulacral feet conical, simple j ventral with terminal suckers, supported by 
calcareous rosettes, the walls of both supported by cribriform plates. Peri- 
stome large, edge entire, without branchial notches, the peristomal mem- 
brane uniformly plated with twenty rows of imbricating scales, correspond- 
ing with the rows of plates of the test, and the rows of ambulacral feet con- 
tinued over them to the edge of the mouth. Periproct large ; ovarian plates 
large, sometimes broken up into several pieces ; ovarian pores large, partly 
filled up with membrane. Dental pyramid wide, strong, and low ; the epi- 
physes of the tooth-sockets do not form closed arches ; teeth simply grooved. 
Spines hollow, small, the larger (and also the pedicellaries) approaching in 
character to those of the Diadematinm. Wyville Thomson (22). 
Phormosoma, g. n., W. Thomson. Plates of the test only slightly over- 
lapping, and fitting so closely as to form a complete calcareous casing, with- 
out any membranous fenestrse ; dorsal and ventral surfaces differing singularly 
