ANODONTA. 531 
of his description: “umbo much eroded, exhibiting a chalky-white stratum, then a 
dull wax-yellow surface,” and “ anterior margin equally rounded with the posterior 
margin.” ‘The first-mentioned character is also to be found in A. extlior, Lea, from 
Vera Cruz, but not in A. chapalensis (coarctata); this latter, which also inhabits 
Central Mexico, may be known from A. chalcoensis by the very different form of 
the anterior and posterior extremities. Moreover, the measurements given by Say }, 
breadth (=long.) less than two inches (50 millim.), height 248; inches (=33 millim.), 
and convexity (diameter) less than 7%; (17 millim.), agree well with Fischer and Crosse’s 
figure of A. chalcoensis 5. 
Tacubaya is a hamlet in the immediate vicinity of the Mexican capital, and a little 
to the west of it. 
The Lake of Chalco is the eastern portion of the great freshwater-basin in the 
southern part of the elevated plateau of Mexico, and artificially separated from the 
western portion, the Lake of Xoibimilco; it has no open drainage, either to the 
Atlantic or to the Pacific Ocean. 
6. Anodonta lurulenta. 
? Anodon lurulentus, Morelet, Test. Noviss. i. p. 28 (1849) *. 
Anodonta lurulenta, Fisch. & Crosse, Miss. Scient. Mex., Moll. ii. p. 523, t. 64. figg. 6, 6a”. 
Anodonta strebeli, Lea, Proc. Acad. Phil. 1868, p. 150°; Journ. Acad. Phil. (2) vi. p. 122, 
t. 52. fig. 185 *,=Obs. Gen. Unio, xii. p. 82, t. 52. fig. 185°; Clessin, in Martini & 
Chemnitz, Syst. Conch.-Cab. ed. 2, Anodonta, p. 138, t. 42. figg. 5, 6 (copied from Lea) ° ; 
Fisch. & Crosse, loc. cit. p. 5247. 
Oval-oblong, produced before, subrostrated behind, green, with numerous narrow rays, according to Fischer 
and Crosse shining in the fore half, sublamellated in the hinder half. 
a. Long. 54; alt. vert. 294, ale 303, diam. 19 millim. Vertices in 3 long. 
by AO; 3 22, , 23, 4, +153 ,, ” 2, 
Hab. E. Mexico: Vera Cruz (Strebel =~"). 
Yucatan: San Gerénimo (Morelet *). 
N. Guaremata: marshes of the Rio Usumacinta (Morelet '). 
The identity of Morelet’s and Fischer and Crosse’s specimens, at first sight, seems 
doubtful, as Morelet gives a different lecality to that indicated on the tablets on which 
Fischer and Crosse’s examples are fixed, and also a different height to the shell 
(47 millim.), whereas the length he mentions is the same as that of Fischer and 
Crosse’s specimens (53-54 millim.); 7. é., in Morelet’s description the height is eight- 
ninths of the length, in Fischer and Crosse’s description and figure five-ninths. If 
Morelet’s measurement is correct, his species must be quite different. E. Smith, however, 
informs me that there is no specimen corresponding to the height mentioned in Morelet’s 
collection, now in the British Museum, and that of the three examples representing 
A. lurulenta, the largest is evidently the shell figured by Fischer and Crosse, these 
being marked “ Marais de S. Geronimo, Yuc.”; he thinks, therefore, that “altitud 4% 
must be a typographical error for “ altitud 31.” ae 
