52 URECHINUS NARESIANUS. 
Pourtalesia miranda A. Ac. 
Off Havana, Grenada. 242-576 fathoms. 
The fragments of other Pourtalesife, dredged principally off the Barbados 
to which I referred in Bull. M. C. Z., VIII., No. 2, p. 80, 1880, belong prob- 
ably to the genei'a Cystechinus and Spatagocystis. The fragments are too 
imperfect for determination, and have no value beyond the fact that they 
indicate the presence of other species of the group in the West Indies. 
Urechinus naresianus A. Ag. 
Lesser Antilles, Lat. 41° 24' 45" N., Long. 65° 35' 30" W. 422-1242 fathoms. 
PI XXVI. Figs. 1-3. 
The greater part of the specimens collected by the Blake measured 
about 30 mm. in length, but varied greatly in heiglit. They agree quite 
closely with what I have designated as the normal stage in the Report of the 
Challenger Echini. (See Chall. Ech., PI. XXX^ Figs. 7-9, p. 146.) The 
specimens examined all show but three genital openings. The structure of 
the subanal fascicle shows that in this genus it assumes all the stages of de- 
velopment intermediate between a well-defined subanal plastron, such as is 
figured on Plate XXX". of the Challenger Echini Report, and a stage in 
which this fasciole is indicated merely by irregular accumulations of mili- 
ary tubercles. So that the genus Urechinus is the representative of the 
oldest Spatangoids with a disconnected apical system, large ambulacral and 
interambulacral plates with simple linear ambulacral pores, in which the 
subanal fasciole (the only one existing) is still in process of formation ; this 
type of Spatangoid leading us little by little to Spatangoid genera in which 
the ambulacra become more or less petaloid, as in Ilomolampas, Paleopneus- 
tes, and the like, till we get the modern type of Spatangus proper, with, 
well-defined petaloid ambulacra, and a highly developed subanal fasciole, 
the lateral fasciole existing in some of these genera, Paleopneustes, Lino- 
pneustes, Calymne, Maretia, etc., in a rudimentary form, as accumulations of 
miliary tubercles along the ambitus. On the other hand, a slender peripeta- 
lous fasciole is in some genera, Paleopneustes, Ilomolampas, Rhinobrissus, 
etc., developed as a slender thread, or as a more or less well-defined fasciole 
extending across the termination of the more or less rudimentary petals. 
We find the lateral fasciole developed from the peripetalous fasciole in 
