298 Annals of the Carnegie Museum. 



Alasmidonta and Strophitus. It has the beak-sculpture 30 of the genera 

 of the Alasmidonta-group, and approaches Strophitus in the hinge. 

 It is very much to be regretted that gravid females are not at hand, 

 and that the structure of the charged marsupium and the glochidia 

 remain unknown. The sterile females, which I have seen, make 

 it clear that only the outer gills are used as marsupia, and that they 

 have a structure like that found in sterile females of the Anodontince. 

 in general. 



Lastena lata (Rafinesque). 



I have received, from B. Walker, the soft parts of two males and 

 two sterile females from the Cumberland River in Pulaski and Cumber- 

 land Cos., Kentucky. 



Anal and supra-anal separated by a rather short connection of the 

 mantle. Anal finely crenulated, branchial with papillae. Posterior 

 margins of palpi connected for a short distance. 



Gills and gill-diaphragm normal, and not as described by Simpson. 31 

 Gills long and rather narrow, the inner one decidedly wider in front, 

 its anterior end distinctly in front and below the anterior end of the 

 outer gill, but separated from the palpi by a short, but distinct interval 

 (it is connected with the descending part of the mantle attachment 

 line for about three-fourths of its length, while one-fourth is occupied 

 by the interval). Posteriorly, the gills do not project freely, but are 

 entirely of the usual shape. Inner lamina of inner gills free from the 

 abdominal sac with exception of the anterior end. 



Septa and water-tubes normally developed. Marsupium formed 

 by the outer gills, with the water-tubes narrow, and the septa close 

 together, thick, and with strongly wrinkled epithelium. In the females 

 at hand, no indications of secondary water-tubes could be seen. The 

 thickened tissue at the edge of the gill was also not well developed. 

 Both specimens are small (under medium size, about 40 and 45 mm. 

 long), and seem never to have been gravid. 



Color (of alcoholic material) whitish, edge of mantle brown, black 

 behind. 



30 This sculpture is somewhat variable. It begins with simple concentric bars 

 upon which a few heavier bars follow, slightly sinuated in the middle and angled 

 behind, and then follow a few more upon the disk, quite heavy, but indistinct. 

 The latter are sometimes absent, and sometimes even the sinuated bars are very 

 rudimentary. The sculpture resembles somewhat that of Strophitus. 



31 Simpson (19006, p. 654) says: "inner and outer (gill) about alike in size and 

 form, projecting free slightly behind." 



