294 KANSAS UNIVERSITY SCIKSCE BULLETIN. 



Fallaciosa stands very close to anodontoides, and may yet 

 be regarded as a variety of that form. The latter is a heavier, 

 coarser shell, with a more pronounced umboidal ridge, less 

 umboidal sculpture, and a duller color than falfacioxa. 

 The relation of the height to the length of the shell of 

 anodontoide* in a series of Kansas shells was 1: 1.95; the 

 similar relation in fallaciosa was 1 : 2.30. The shell of the 

 latter is much more brilliantly rayed and the female is more 

 produced. Simpson states there is a horny raised ridge on 

 the inside of the mantle behind which is not present in speci- 

 mens of anodontoides. 



Lampsilis recta Lamarck. Plate LXVI, fig. 2. 



Unio recta Lamarck. An. sans Vert., vi, 1819, p. 74. 



Shell large, thick, thickest anterior to the umbones, elon- 

 gate, moderately compressed, females produced posteriorly. 

 Anterior margin nearly circular ; ventral very slightly bowed, 

 much produced in females ; posterior margin pointed at an 

 extremely variable angle ; dorsal margin slightly curved and 

 meeting the posterior at an approximate angle of 160 degree3. 

 Umboidal ratio, from 0.16 to 0.22. Umbones small and full, 

 marked with fine concentric ridges. Anterior and lateral 

 slopes rounded. Umboidal ridge prominent and continuously 

 rounded. Posterior umboidal slope narrow and abrupt. 

 Epidermis smooth and shiny, very dark brown to blaek in 

 adult shells ; young shells marked with wide olive-green ravs 

 over the entire shell; old shells eradiate. Lines of growth 

 numerous, rounded, continuous. Ligament long, stout, dark 

 brown. 



Interior: Pseudocardinals, high, erect, columnar or high 

 pyramidal except for the left posterior, which is often plate- 

 like, serrate, double in the left and sometimes in the right, the 

 anterior right when developed sharp and spine-like, the pos- 

 terior right large; laterals long, high, straight or slightly 

 curved ; anterior adductor cicatrix of moderate size and ex- 

 cavation, narrow, fan-shaped, sometimes set slightly under the 

 anterior left pseudocardinal ; retractor cicatrix, large and 

 semicircular in outline. Posterior cicatrices of moderate size, 

 lightly impressed, much longer than wide, confluent. Pal- 



