388 Bulletin American Museum of Natural History [Vol. LIII 
Glochidia, as far as observed, were subtriangular in shape and 
without hooks, about 0.23 to 0.25 mm. long, 0.20 to 0.21 mm. high. 
PARREYsIA Conrad 
Parreysia ConRaAD, 1858, Proc. Ac. Nat. Sc. Philadelphia, VI, p. 267. Monotype: 
Unio multidentatus ‘‘Parreyss”’ Philippi. This is said to be a synonym of Mya cor- 
rugata O. F. Miiller of India. 
The name is frequently misspelled Parreyssia. 
Simpson has defined the genus upon shell characters as follows: 
Shell solid, inflated, oval to subrhomboid, with full, high, zigzag, radially sculp- 
tured beaks, the sculpture often extending over the disk; epidermis smooth and bright, 
sometimes a little rayed, with two irregular pseudocardinals in the left valve which 
are more or less broken into ragged denticles or are strongly, vertically striate, and 
two laterals, the lower the larger; right valve with one, sometimes two pseudocar- 
dinals, the upper small, compressed, and a few tubercles behind them, with two 
laterals, the upper the larger; cavity of the beaks rather deep, not compressed; dorsal 
scars under the hinge, not visible; the two upper anterior muscle scars very deep, 
confluent, the lower linear; nacre white to salmon, iridescent behind. (1914, ‘De- 
script. Cat. of Naiades,’ p. 1103). 
It is not known whether the Ethiopian Region mussels which have 
been referred to Parreysia are really related to the Oriental forms for 
which that name was proposed. Their relation to the unionid section 
Cafferia is equally obscure, as there seem to be no definite distinctions 
in the shells. The use of generic names of such uncertain application 
appears to be no advance over the all-embracing use of Unio as in 
former times. 
Frierson (1909, The Nautilus, XXII, p. 107) and Ortmann (1910, 
op. cu., XXIII, pp. 139-140, and 1911, op. cit., XXIV, p. 106) ex- 
amined the soft parts of P. wynegungaensis (I. Lea), an Asiatic species 
closely allied to the genotype. It has essentially the structure of North 
American Quadrula. The anal and branchial openings, the diaphragm, 
the palpi, gills and marsupium are practically identical, as are also the 
general shape and insertion of the gills (the inner separated from the 
posterior end of the palpi). The only differences are, that the supra- 
anal opening is rather widely separated from the anal, and that the inner 
gills are entirely connected with the abdominal sac. In the female all 
four gills serve as marsupium. B. Prashad has published additional 
observations on the anatomy of some of the Indian species. He gives the 
following summary of the animal of Parreysia: 
eee 
11918, The Nautilus, XX XI, pp. 75-76. 
