108 THE NAUTILUS. 



and distinguish Spatha at a glance from the North American shells, 

 as well as from the Asiatic Parreysia and Lamellidens, while, as we 

 shall see by comparison with South American shells, the shape of the 

 palpi, and the special structure of the water tubes is not so import- 

 ant, and while, in the development of the anal and supra-anal open- 

 ing, there are differences also in the South American shells. 



SOUTH AMERICAN FORMS. 



The following observations are new, and so it seems advisable, to 

 give a more complete description of the structure of the soft parts of 

 some of these forms. 1 select as the first, and most important, the 

 type -gen us of the Hyriince. 



Hyria corrugata Lamarck. Two specimens are at hand, both 

 females, the one sterile, the other gravid, with eggs. They have 

 been collected by Mr. J. D. Haseman on Dec. 10, '09, on a sand 

 bar in Rio Tapajos, at Santarem, State of Para, Brazil. (See pi. 

 vii, fig. 6, and pi. vi, fig. 6). 



Anal opening closed above by the connection of the inner mantle 

 edges without forming a supraanal opening, closed part about twice 

 as long as the anal opening. 1 Anal opening a little shorter than the 

 branchial opening, separated from the latter by the solid union of the 

 inner mantle edges. Inner edge of anal opening almost smooth, of 

 the branchial opening with small papilla?, which stop suddenly ante- 

 riorly, thus marking the anterior boundary of the branchial opening. 

 In front of this the inner mantle edges are smooth and perfectly un- 

 connected. (There is nothing like " short, contractile siphons," as 

 Simpson states on the authority of J. E. Gray, unless it should be 

 that the inner edge of the anal is capable of expansion.) 



Palpi longer than wide, not falcate, although slightly produced 

 posteriorly, and bluntly pointed, not connected on the posterior 

 margin. 



(To be continued.) 



1 Under the closed part extends the supraanal canal, exactly as in Spatha, 

 although von Ihering asserts (Zool. Anz. 15, '92, p. 2) that in the South Amer- 

 ican Unio (which includes ffyrta, etc.) there is no such canal, and that the 

 mantle edge is affixed to the adductor muscle. The latter is impossible, since 

 there is the rectum above the adductor. 



