26 University of Michigan 



U. triangularis Raf. =U. lateralis Raf. = f/. sintoxia Raf. = f/. 

 pachostca Raf. =: U. mytiloides Raf. ^ {7. rubra Raf. = [/. pyramida- 

 tus Lea, Conrad, '34, p. 72. 



[7. scalenius Raf. = f/. cuneata Raf. = L''. patuhis Lea, Conrad, '34, 

 p. 71. 



L'. cuneatus Raf. = patulus Lea. Ferussac, '35, p. 28. 



[/. mytiloides Raf. = t/. pyramidatus Lea = (7. rubra Raf., Ferus- 

 sac, '35, p. 28. 



f/. c/az'a Lam. = U. scalenia Raf., Ferussac, '35, p. 28. 



U. clava Lam.= U. scalenius Raf., Conrad, '35, p. 5, pi. 3, f. i ; 

 Lea, '38, p. 126. 



U. mytiloides Raf. = U. rubra Raf. = U. pyramidatus Lea, Conrad, 

 '36, p. 41, pi. 20. 



Cunicula patula (Lea), Swainson, '40, p. 378. 



Pleurobema clava (Lam.) and PI. mytiloides (Raf.), Agassiz, '52, 

 p. 49. 



Pleurobema clava (Lam.), Simpson, '00c, p. 745; '14, p. 735. 



Pleurobema clava (Lam.) = 17. elliptica Rai. = Obi. scalenia Raf. 

 = PI. cuneata Raf., Vanatta, '15, p. 555 ("types" examined). 



The original description of U. clava Lam. is very poor; how- 

 ever, a "sublongitudinal, oviform shell, with the anterior (pos- 

 terior) side very short," cannot be referred to any other Amer- 

 ican species. The short anterior side (indicating the anterior 

 position of beaks) is very characteristic. This identification 

 is confirmed by Lea's examination of the type. The original 

 locality (Lake Erie), given by Lamarck, is erroneous. 



PI. mytiloides Raf. has been taken by Conrad and others to 

 be U. pyramidatus, but it is clearly recognizable from Rafin- 

 esque's description and figure. The latter, as usual, is exag- 

 gerated, but distinctly represents a phase frequently assumed 

 by clava, chiefly when old. It cannot be pyramidatus on 

 account of the presence of distinct rays. The recognition of 

 mytiloides has no bearing upon the nomenclature of the spe- 

 cies ; it is, however, important for that of the genus (see 

 above). 



The identification of scalenia Raf. with this species is evi- 

 dent from the original description and figure and is confirmed 



