ORTMANN: FAMILIES AND GENERA OF NAJADES. Arle 
own line, which is also indicated by the full development of the beak- 
sculpture. It may be possible, that species forming connecting links 
with Fusconaja still exist in eastern Asia. The investigation of ad- 
ditional, related types is much to be desired, and we should try 
especially to become acquainted with the glochidia. 
Parreysia wynegungaénsis (Lea). 
A number of specimens from Bombay, India, have been sent to me 
by L. S. Frierson. As to the description, I refer to my previous pub- 
lications (Ortmann, I910), p. 139, and 19IIa, p. 106, pl. 6, fig. 4, 
ply 7, hg: 3)- 
Genus LAMELLIDENS Simpson. (1900.) 
Simpson, 1900), p. 854.—Ortmann, I19IIa, p. 106. 
This genus bears about the same relation to Parreysia, as does 
Unio and Elliptio to Fusconaja and Quadrula. A complete diagnosis 
cannot be given at the present time, but the differences known to 
exist in the only species examined are the following: Outer gills alone 
marsupial, the shell more elongated, with the beak-sculpture rudi- 
mentary. 
As to the latter character, I may mention that I have seen, in a 
specimen of L. consobrinus, as well as in specimens of L. marginalis 
(Lamarck) in the Carnegie Museum, that the sculpture starts with a 
few (one or two) fine, concentric bars, and, following these, other bars 
are added, of which, however, only the lateral (anterior and posterior) 
parts are developed, which assume a direction radiating from the 
anterior and posterior side of the beak. These radiating ridges are 
very short, and I think they give us a clue as to the derivation of the 
radiating sculpture from the concentric. I think the Lamellidens- 
sculpture represents a phylogenetically older stage of beak-sculpture, 
while in other characters the form investigated is somewhat more 
advanced. 
Lamellidens consobrinus (Lea). 
One single sterile female from India has been investigated; I re- 
ceived it from L. S. Frierson. For the anatomy see my previous 
publication (Ortmann, I91Ia, p. 106, pl. 7, fig. 4). 
