UNIO. 515 
Unio plexus, Conrad, Monogr. Fam. Unionide, p- 89, t. 49. figg. 1, 2 (1838) *. 
Unio coloratus (Charpentier), v. Mart. Malak. Blatt. xii. p- 59 (1865)°; Fisch. & Crosse, loc. cit, 
p- 599*° (part.). 
Thick-shelled, elliptical, rather swollen ; outside unicolorous deep black, with few and not very conspicuous 
plaits on the hinder slope, most of them directed obliquely backward, those in the middle of the shell 
Sometimes directed vertically downward ; inside purple, passing into orange. 
a. Long. 64; alt. vert. 34, alee 35, diam. 26 millim. Vertices in 2 long. 
86; .,, 982, 314, 24 
eo . bl; ,, 29, ,, 262, 
d, 29 50; 2” 29, ” 273, ” 22 ” 
é. ” 443; ” 253; 5) 263, 
J: 9 42; ” 24, ” 24, » Li ” 
g- 9» 423 ; ” 233, 9 24, 455 73 ” ” 3 9 
a, An unusually large specimen collected by H. Strebel; 6. Uhde’s example®; c, d. Specimens collected by 
H. H. Smith; ¢, f, 9, by Strebel. All from the Rio Medellin. 
Hab, EK. Mexico: Rio Medellin, near Vera Cruz (Uhde®, Strebel, H. H. Smith) ; Rio 
Jamapa, near Vera Cruz (Strebel, in Mus. Hamburg) ; Mexico, without nearer 
indication of locality (Dr. Burrough ' ?). 
9 29 99 
9 
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bee Oop Coe We Cale Be 
I have given the measurements of several specimens from the Rio Medellin, in order 
to show the range of variation in shape, the height of the summits in some of them 
being a little more, in others a little less, than that of the wing, and the proportion of 
the height to the length varying also considerably. 
Lea 1? gives the colour of the inside as nacre-purple, rarely white ’, and in his figure 
it is white. Out of fifty-six examples before me, two only, both also from the Medellin 
river, are white inside, one of them perhaps bleached, the other fresh. The purple is 
not of the same tint as in U. aztecorum and others, but more lustrous and somewhat 
verging into orange. 
Burrough’s specimens also were probably from the Medellin river, as this locality is 
expressly mentioned by him for the var. carbonarius. 
Var. minor. (Tab. XXXIX. figg. 4, 4a.) 
Unio pliciferus, var. minor, Fisch. & Cross, loc. cit. p. 581, t. 69. fig. 4". 
Only differing by its smaller size. 
h. Long. 33; alt. vert. 214, ale 22, diam. 16 millim. Vertices in 2 long. 
Ve 9 35 > ” 193, ” 21, ”? 12 ” ” 3 9 
} ” 33% 3 ” 20, 3 20, 1 14 ” . ” 3 ” 
Ba 855 a 17 ds oe LE » 3 
L ” 32 ; ” 16, ,; 18, ,, 12 ” ” 3 » 
m 28 ; 9 14, 5 14,3, 10 ” ” 3 
ah Bacher and Crosse’s figure"; ¢. Specimen received from Anthony ; jy k, and 1. Examples collected by 
H. Strebel; m. Specimen in the late Dunker’s collection, now in the Berlin Museum—notwithstanding its 
small size, probably full-grown, as the shell is comparatively solid and the summits much worn. 
Hab. E. Mexico: with the typical form ( Fischer & Crosse +"); Rio Medellin (Anthony, 
H. Strebel). 
65* 
