506 MOLLUSCA. 
d. coloratus. 
Unio coloratus (Charpentier), Kiister, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Unio, p. 155, 
t. 44. fig. 6 (1856); Fisch. & Crosse, loc. cit. p. 599 (part.) ». 
More abbreviated, with slightly convex dorsal margin and straight ventral margin. 
Long. 49; alt. vert. 28, ale 28, diam. 18 millim. Vertices in ;%; long. 
Hab. Mexico, without nearer indication of locality (Charpentier). 
e. subventralis. (Tab. XXXVI. figg. 1, 1 a, 6.) 
Ventral margin distinctly convex. 
Long. 55; alt. vert. 29, ale 29, diam. 18 millim. Vertices in ? long. 
Hab. S.E. Mexico: Tabasco (Parreyss, in coll. Dunker, nune Mus. Berol.). 
f. arcuans, 0. 
Unio calumitarum (“ ovata ’’), Morelet, loc. cit.” 
Unio calamitarum, Sowerby, in Reeve’s Conch. Icon. xvi., Unio, t. 14. fig, 385”. 
Unio calamitarum, var. arcuans, Fisch. & Crosse, loc. cit. p. 612, t. 64. figg. 5, 5a”. 
Abbreviated, posterior dorsal margin elevated and arcuated. 
Long. 47; alt. vert. 25, alee 28, diam. 17 millim. Vertices in + long. 
” 43 ; 9 22, 29 25, of ? + 
” 9 Fe) 
Hab, S.E. Mexico: in the stream Baluntie, near Palenque (Morelet ?!). 
This species corresponds to the section Simonaias of Fischer and Crosse. Morelet 
noted its variability in outline, and on this character Fischer and Crosse distinguished 
several varieties, though they maintain the species described by other authors as 
distinct. Lea!? describes the ventral margin of his U. cuprinus as “ disposed to 
be straight,” and the general form as “reversely ovate,” but the figure given by him 
shows the ventral margin to be distinctly sinuate, and the general outline kidney- 
shaped, not ovate; it seems, therefore, that he also had specimens of different outline 
before him. As it is not possible to say which form is really the type of U. cuprinus, 
I have treated each of them as a variety, and quoted only the general descriptions, 
which comprise several forms, under the head of the species, just as I have done with 
Pachychilus glaphyrus, antea, p. 438. Sowerby’s figure 385°? corresponds, on the 
whole, to the var. arcuans, but it has the ventral margin sinuated, and thus forms a 
link to the var. nephriticus. 
/ 
i 
ff 
/ 
30. Unio dysoni. 
? Unio rugulosus (Charpentier), Kiister, in Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, Unio, 
p. 154, t. 44, fig. 5 (1856) *. 
Unio dysoni, Lea, Proc. Acad. Phil. 1859, p. 152°; Journ. Acad. Phil. (2) iv. p. 252, t. 89. 
fig. 182°; Obs. Gen. Unio, vii. p. 70, t. 39. fig. 132°. 
Near U. cuprinus, but more produced before, more rounded behind and below ; inside whitish. 
Hab. Honvvuras (Dyson *~*). 
