524 PATAGONIAN EXPEDITIONS I 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 Lymncea 

 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. 



FIG. 4. 



Marginal teeth of Lymn<za stagnalis L. Two outer lateral and two inner marginal 



(after Dybowski). 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 Lymnaeid teeth may be found in the following works, among others : 



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

 i873,Taf. 15, 1 6. 



J. Hazay : Malak. Blatter, n. F., VII, Taf. i {Lymncea auricidaria, ovata, peregra). 



W. Dybowski : Studien iiber die Zahnplatten der Gattung Limnsea Lam., in Bull. Soc. Imp. 

 Naturalistes de Moscou, LX, 1884, pt. 2, pp. 256-262, pi. 5 (L. stagnalis var. vulgaris). The 

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

 (Amphipeplea glulinosd). 



R. P. Whitfield : Description of Lymncea (Bulimncea) 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 Limnseas 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. haivaiiensis). 



