THE NAIADES OF MISSOURI l8l 



the most beautiful shells. It is strange that it shoud not be found 

 anywhere in the Ozarks as it seems to be a mussell that rather 

 prefers swift current. Yet as that is an unglaciated region without 

 much sand, to which it is partial, we may account for its absence 

 there in part. It is entirely supplanted in the Osage hy J allaciosa. 

 From the writer's breeding record for this species it is bradytictic. 



Lampsilis f allaciosa Smith. 



("Slough Sand Shell," "Creeper.)" 



PI. VII, Figs. i8 A and B. 



1899 — Lampsilis fallaciosa Smith, Bull. U. S. Fish., p. 291, pi. LXXIX; 

 1900a, Simpson, Pr. Ac. N. Sci. Phila., p. 74, pi. II, fig. 5. 



Animal Characters: — Identical with L. anodontoides in 

 every respect, except perhaps in glochidial characters. 



Shell Characters: — Differs from anodontoides in possessing 

 a smaller, lighter, thinner shell; a more prominent post-umbonal 

 ridge; more pronounced beak sculpture; pinkish nacre in umbonal 

 cavity; bright yellowish, or olivaceous epidermis with bright 

 green rays all over shell — especially on the posterior slope; rusty 

 red color often for umbonal region ; a sulcus often seen just anterior 

 to the post-ventral edge and extending a short distance up on the 

 shell as a radial furrow. 



Sex Length Height Diameter Locality 



mm — (Lower L. Contrary, St. Joseph) 

 mm — (Chariton R., Kern) 

 mm — (Miss. R., Hannibal) 

 mm — (Osage R., Warsaw) 

 5.5mm — (Grand R., Chillicothe) 



The last measurement is that of a juvenile identified by Dr. 

 Howard. Its beaks are sculptured by two or three subparallel 

 ridges at the base of the post umbonal slope and a few very faint 

 tubercles at the base of the anterior umbonal slope. Anterior end 

 of the shell is greatly produced as noted in most juvenile shells 

 of any species. Note the very small inflation in the above measure- 

 ment. It is strange that this shell at this stage of its life should be 

 practically rayless while the rayed character of the adult shell is 

 its chief feature. 



Miscellaneous Remarks: — Fallaciosa may have developed 

 from anodontoides for ecological reasons. This little striped shell 



