MUSEUM OF COMPARATIVE ZOOLOGY. 281 
Cetoconcha the ventral body wall externally gathered along a line into pinched- 
up lamin which develop at opposite ends of a lateral line, with a supplemen- 
tary second line corresponding to the branchial appendix ; finally, the posterior 
consolidation of the series into a small gill free from the ventral surface except 
at its proximal extremity, as in Lyonsiella and Verticordia. 
The incurrent siphon is long, retractile into the cavity between the sides of 
the mantle, the excurrent siphon much shorter; around their bases is a series 
of stout (in C. elongata arborescent?) darkly pigmented tentacular appendages, 
with smaller papille inside from them, but no visible ocelli; the mantle from 
below the mouth backward is open for two thirds the distance to the siphons, 
a marked distinction from Verticordia and its congeners ; its margin is plain 
and not very stout ; the intestine passes through the heart, below which are 
two glandular brown feather-shaped renal organs; the liver, ovaries, and 
muscles are well developed, but a large part of the body cavity is vacant, and 
its walls are sustained by mesenteric bands or fibrille# attached to the adduc- 
tors or the dome of the shell. Type Lyonsia bulla Dall. 
The remarkable characters of this group will be sufficiently evident to those 
who have a fair knowledge of the macroscopic anatomy of the Pelecypods. 
Especially do the gills attract attention, and enforce the lesson of the muta- 
bility of these breathing organs, and their unfitness for use in fundamental 
classification. 
To Poromya as restricted belong P. granulata Nyst, P. sublevis Verrill, P. 
neerovdes Seguenza, and P. australis and probably P. levis Smith. 
To Cetoconcha belong C. bulla Dall, C. tornata (Pecchiolia) Jeffreys, C. nitida 
(Thracia) Verrill, and C. elongata, albida, and margarita, new species. 
The shells grouped by Deshayes, in his discussion of the molluscan fossils 
of the Paris basin, under the name of Poromya, form a very heterogeneous 
assembly, which, in the absence of typical material, would be difficult to 
assort properly. 
Poromya granulata Nyst and WestEenporpr. 
Poromya granulata Nyst and West., Dall, Bull. M. C. Z., IX., p. 108, 1881. 
Corbula granulata Nyst and West., Nouvelles Res. des Cog. Foss. d’Anvers, p. 6, 
pl. iii. fig. 3, 1859. 
P. anatinoides Forbes, Hgean Rep., 1844, p. 103. 
Habitat. Sand Key, 15 fms.; Station 36, 84 fms.; Station 9, 111 fms.; 
Station 5, 229 fms.; off Sombrero, 72 fms.; temperatures at bottom 49°.5 to 
60°.0 F, 
Variety P. australis Smith.* 
Habitat. Barbados, 100 fms.; off Sombrero, 54 fms.; Station 20, off Bahia 
Honda, Cuba, in 220 fms., living, bottom temperature 62°.0 F.; Station 262, 
off Grenada, in 92 fms,, sand, same temperature. 
* Poromya australis Smith, Chall. Lam., p. 54, pl. xi. figs. 2 a, 2b, 1885. 
