THE NAUTILUS. 



VOL. XXX. DECEMBER, 1916. No. 8 



THE ANATOMY OF THE NAYAD HYRIOPSIS MYEKSIANA (LEA). 



BY DR. A. E. ORTMANN. 



Hyriopsis myersiana (Lea). Simpson, Descript. Catal. 1914, 

 p. 212. 



The Carnegie Museum of Pittsburg has received, from Dr. B. 

 H. Bailey (Cedar Rapids, la.) two shells with the soft parts, 

 and the soft parts of a third one. One of these with shell is a 

 a female, the others are males. They were collected by Dr. E. 

 B. McDaniel at Petchaburi, Siam. 



The genus Hyriopsis Conard, 1853, has been defined only by 

 shell characters, and the anatomy was unknown hitherto. 

 Simpson (1. c. p. 207) has placed it in the vicinity of Lamp- 

 silis, apparently relying on the similarity of the shell to that of 

 Lampsilis (Proptera) alata (Say), which is a Lampsilis shell. 



The soft parts at hand exhibit the following characters : 



Branchial opening separated from the anal by a complete gill- 

 diaphragm, but not by a mantle-connection. Anal and Supra- 

 anal openings of about the same length, separated from each 

 other by a well developed mantle-connection of moderate length, 

 shorter than either. Anal opening with inner edge nearly 

 smooth ; Branchial opening longer than the anal, with strong, 

 irregular papillae on inner edge. In front of the Branchial, the 

 inner edge of the mantle becomes smooth. Palpi subfalciform, 

 long, posterior margins connected for about half their length, 

 and connected with the inner face of the mantle for about one 

 third of their length. 



