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. diaphaiia differ from those of typical LymncBa 

 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 Lynnncea [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 Lymitcsa stagnalis L. 

 (after Dybowski). 



Two outer lateral and two inner marginal 

 teeth of Lytmuva patagonica liochicoensis Pils. 



LymncBa 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 w^hich 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.^ 



' Figures of Lymnajid 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, 16. 



J. Hazay : Malak. Blatter, n. F., VII, Taf i {Lyiiin(ea ojiricularia, 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 (Z. stagnalis var. vulgaris). The 

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

 {A)nphipeplca glutinosa). 



R. P. Whitfield : Description of Lymncea {Bulinmcea) megasonia Say, in Bull. Amer. Mus. Nat. 

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



Fischer et Crosse : Mission Scientifique au Mexique, Mollusques, II, pl. 36 (Z. aiiriatlaria). 



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 (Z. haivaiiensis). 



