LIMN AA. 377 
forms it is somewhat castaneous; moreover, in these last-mentioned species there is 
often a distinct dark red band inside the aperture in full-grown specimens, of which 
there is no trace in L. attenuata. The surface of the shell of ZL. attenuata is also 
smoother and somewhat shining, not so distinctly striate as in that of L. palustris and 
L. refleaa. In full-grown specimens of the Mexican species the aperture is somewhat 
broadly rounded, the external margin being fully arcuated, and in some examples even 
angularly bent. The columellar fold is generally very distinctly twisted, and the 
columellar margin has a free edge below, not appressed to the surface of the last 
whorl, thus exhibiting a more open umbilical cleft than usual in the European 
L. palustris. 
To show the individual variation in the form of the shell, I give here a series of 
measurements taken from specimens in the Berlin Museum: it will be seen that the 
breadth of the last whorl varies from + to 3, and the length of the aperture from 4 to 
somewhat less than 3, of the whole length, and also that the length of the aperture is 
usually greater than the breadth of the last whorl, rarely equal or even a little less (d). 
Breadth 
a a 
shell. whorl. penultimate aperture. whorls. 
millim. millim. millim, millim. 
rr 33 11 6 12 83 
Boveeeceeee ees 322 8 5 aes 7 
Coveccvveeveee 23 94 54 10 74 
re 22 93 5 9 7 
© leeeeeeeees 99 gi 5 94 7 
foiccccceaeee 29 72 5 9 7 
Yo vevececeaes . 2 9 5 9 7 
ho vvvececeenes 20 5A 4 8 7 
bocce cececeues 18 8 41 9 62 
| re 18 7 4 8 74 
Cove cece ee ene 17 6 43 9 63 
‘The specimen J is decidedly, and 7 probably, not full-grown ; but 4, though remark- 
ably small, is apparently full-grown, showing a somewhat thickened external margin 
and a very conspicuous callus on the columellar wall. 
° ° /) —P Ny _A 
9, Limnea palmeri, = Keclige polinerr - 
Limnea palmeri, Dall, Am. Journ. of Conch. vii. p. 185 (1871)’; Fisch. & Crosse, Miss. Scient. 
Mex., Mollusca, ii. p. 51°. bomewtte 
Gel GV UE Hote Nh, 
Hab. N.W. Mexico: River Yagqui, , south of Guaymas, State of Sonora (Hdw. 
Palmer *?). 
Allied to L. megasoma, Say. According to Dall', the incised lines, very round 
whorls, and deeply channelled suture are its distinguishing characters. 
BIOL. CENTR.-AMER., Terr. and Fluviat. Mollusca, February 1899. 48 
v~ 
