524 



PATAGONIAN EXPEDITIONS: ZOOLOGY. 



parallel to the long axis of the tooth, and are split into a comb-like series 

 of denticles. 



The marginal teeth of L. diaphana differ from those of typical Lymncza 

 by their prostrate position, the cusp of one tooth overlying the basal plate 

 of the succeeding one in the same transverse row, and also by the comb- 

 like cusps. In typical Lymncea (L. stagnalis, fig. 3) the cusp stands 

 obliquely erect, its cutting edge transverse to the long axis of the tooth. 



48 



FIG. 4. 



Marginal teeth of Lymncea stagnalis L. 

 (after Dybowski). 



Two outer lateral and two inner marginal 

 teeth of Lymncea patagonica riochicoensis Pils. 



Lymncea patagonica riochicoensis (fig. 4, two outer lateral and two inner 

 marginal teeth) has a radula closely resembling that of L. diaphana. 

 There are ten lateral teeth. 



No Lymncea of the northern hemisphere, of which the teeth are known, 

 has marginals like those of L. diaphana, but I have shown that some- 

 what similar teeth exist in a Hawaiian species. 1 



1 Figures of Lymnseid teeth may be found in the following works, among others : 



Lehmann : Die lebenden Schnecken und Muscheln der Umgegend Stettins und in Pommern, 

 1873, Taf. 15, 1 6. 



J. Hazay : Malak. Blatter, n. F., VII, Taf. I (Lymncea auricularia, ovata, peregra). 



W. Dybowski : Studien uber die Zahnplatten der Gattung Limnaea Lam., in Bull. Soc. Imp. 

 Naturalistes de Moscou, LX, 1884, pt. 2, pp. 256262, pi. 5 (L. stagnalis var. vulgaris). The 

 best figures of Lymncea teeth published. Also, Malak. Blatter, n. F., VIII, p. 124, Taf. 7 

 (Amphipeplea glutinosa). 



R. P. Whitfield : Description of Lymncea (Bulimnced) megasoma Say, in Bull. Amer. Mus. Nat. 

 Hist, I, 1882, p. 29, pi. 5. 



Fischer et Crosse : Mission Scientifique au Mexique, Mollusques, II, pi. 36 (L. auricularia). 



F. C. Baker : A revision of the Limna^as of northern Illinois, in Trans. St. Louis Acad. Sci., 

 XI, 1901, pp. 1-24. 



H. A. Pilsbry : Proc. A. N. S. Phila., 1903, p. 790 (L. hawaiiensis). 





