Ortmann; Families and Genera of Najadi - l* 7 < 



own line, which i> also indicated by the lull developmenl 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 wynegungaensis (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, 1910ft, p. 139, and 1911a, p. 106, pi. 6, fig. 4, 

 pi. 7, fig. 3). 



Genus LAMELLIDENS Simpson. (1900.) 

 Simpson, 1900ft, p. 854. — Ortmann, 1911a, p. 106. 



This genus bears about the same relation to Parreysia, as does 

 Unto and EUiptio to Fusconaja and Qiiadrula. 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, 1911a, p. 106, pi. 7, fig. 4). 



