MUSEUM OF COMPARATIVE ZOOLOGY. 81 
the temperate and tropical American shores. Some of the genera of the 
family extend into deep water on the Atlantic side, but they have not 
been found by the “Albatross” in the Pacific Panamic district. Neither 
Podocidaris nor Coelopleurus was dredged by us. The absence of the 
latter genus is specially noteworthy, as it is found at Mauritius and has 
been dredged by the “Challenger” in the East Indian Archipelago. 
The only Pacific genus found in deep water was Maretia. It should 
be remembered that the genera of Cidaride and of Echinothurie all 
have an extensive Pacific, as well as Atlantic distribution. There were 
no deep-water Nucleolide, although they are found in shallow water in 
the Central American district and in deep water in the West Indian 
fauna. The occurrence of Echinocrepis, Cystechinus and Urechinus, 
types characteristic of the Southern Ocean and Southern Pacific, is 
interesting, associated as they are with Pourtalesia proper, a genus of 
wide geographical distribution, which, as well as Urechinus, is found in 
the Caribbean district. The ubiquitous Schizaster and Brissopsis were 
associated on the Pacific side with Paleopneustes, Homolampas, and 
Hemiaster, as in the West Indian district ; and the remarkable Aérope, 
which has an extensive geograpical distribution, — it is found in the Ara- 
fura Sea and off the eastern coast of North America, —was not un- 
common in the Panamic area. Moira, on the contrary, which again is a 
characteristic American genus on both sides of the continent in the tem- 
perate zone, was not obtained by the “ Albatross” on her present cruise. 
I need at present only to refer to the chapter on the origin of the 
West Indian Fauna in the report of the ‘“ Blake” Echini,? where lists 
will be found of the Cretaceous and Tertiary Echini, and where they are 
compared with those living in the West Indian and neighboring areas at 
the present day. It is interesting to note here the occurrence of a spe- 
cies of Cystechinus from the Radiolarian Marls of Barbados, mentioned by 
Gregory.” I understand from him that a species allied to Paleopneustes 
has also been detected in the same bedse The existence of Cystechinus 
at Barbados is another link in the evidence of a former connection be- 
tween the Caribbean and the Pacific, —of a time when, as I have sug- 
gested, the Caribbean was probably a bay of the Pacific, — until later 
cretaceous times; but they gradually during the tertiary period® became 
1 Mem. Mus. Comp. Zool., Vol. X. No. 1, and Three Cruises of the “ Blake,” 
Vol. I. pp. 92, 109-124. 
2 See Quart. Journ. Geol. Soc. London, November, 1889. 
3 See the Memoir of Gabb on the Geology of Santo Domingo, in the Trans. of 
the Am. Phil. Soc., Vol. XV., 1873, pp. 49-259. 
