L893.] NATURAL SCIENCES OF I'll 1 1, A 1 (EL.PH I A. 395 



Zonitoides ligerus Say. PL 11, Hus. III. IV. 



We have in Pennsylvania and Ohio, a very small form measuring 

 9-10 ram. diameter, which has been considered Z. ligerus, although 

 with some doubt. Besides other differential characters, there are two 

 accessory glands near the head of the dart sac, while W. G. Binnev 

 found only one in typical ligerus. 



No embryo has been secured thus far. The smallest examples 

 found measured about 3 mm. in diameter ; and the radula of one 

 of these is represented in fig. Ill, having 20- c "20 teeth, of which o 

 are perfectly formed laterals and the 7th and 8th nearly so, the 

 latter corresponding with the loth of an adult, and the "transition 

 tooth" 9 to 14. At least 9-13 then, of the younger specimen, will be 

 transformed into laterals. In either example all the teeth showing 

 the transition from the aculeate marginals to the laterals have been 

 represented in my figures, 14-7 in III, 17-11 in IV, 7 so that 

 the transformation can immediately be seen by comparing the 

 teeth bearing the same numbers. We specially notice: first, the 

 total absence of endodonts in all teeth, just as in Z. arboreus ; second, 

 the absence of ectodouts in the distal, newly formed, aculeate teeth — 

 I. e. in most marginals except a few mesial ; and third, the longitud- 

 inally elongated plates of the youngest marginals. 



Besides Z. ligerus, young and adult examples of a few other 

 nearly related species were examined, one from Tennessee probably 

 new, and Z. suppressus Say. They gave essentially the same results 

 as ligerus. 



Patula striatella Anlh. PL 11. figs. VII, VIII. IX. 



Several embryos from the eggs were examined. Fig. IX shows 

 the buccal body of a quite young specimen with the commencement 

 of the radual, in optical section. Diameter of the buccal body 0*12 

 mm. The spindle-shaped cells above are the developing retractor 

 muscle. 



( )f an embryo more advanced, about 1 mm. long, and nearly 

 mature, having a shell of 1 \ whorls, and the caudal bladder small 

 but still slowly contracting, the radula is represented in fig. VIII. 

 It is 44 mm. long, with 21 transverse rows, in the last 9 , c , 9 teeth. 

 But the formation of new teeth is somewhat irregular on the two sides 



7 Fur distinctness tiny arc separated in the drawing; in nature tiny lie close 

 together: this is indicated hv the sisn. 



