498 MOLLUSCA. 
The name “ sagrinatus” is latinized from the modern word “shagreened,” in 
Italian “sagrinato.” I give a figure of a specimen from Managua, in order to 
show the slight degree of inequality between the two valves in this and some allied 
species. 
13. Unio gabbianus. (Tab. XXXIX. figg. 5, 5a, 6.) 
Unio gabbianus, Lea, Proc. Acad. Phil. 1868, p. 95'; Journ. Acad. Phil. (2) vi. p. 295, t. 43. 
fig. 1067; Obs. Gen. Unio, xii. p. 55, t. 43. fig. 106 *; Tate, Am. Journ. of Conch. v. p. 160 
(1870) *. 
Unio nicaraguensis, Lea, Proc. Acad. Phil. 1868, p. 95°; Journ. Acad. Phil. (2) vi. p. 296, t. 43. 
fig. 107°; Obs. Gen. Unio, xii. p. 56, t. 43. fig. 167°. 
Somewhat more oblong than U. cyrenoides, comparatively lower, the concentric ridges not granulated, the 
anterior teeth more feeble ; inside silvery-white. 
a. Long. 39; alt. vert. 264, ale 273, diam. 183 millim. 
b. » 34; ” 25, », 22, 9 ? ” 
- qa, Tea’s measurements of U. gabbianus ; 6, of U. nicaraguensis. 
Hab. Cuntrat Nicaragua: Lake of Nicaragua (Bridges1~* 5-7); north shore of Lake 
Nicaragua (Tate *). 
I cannot find any reliable difference between U. gabbianus and U. nicaraguensis, Lea. 
14. Unio imbricatus. (Tab. XLIII. figg. 6, 6 a-c.) 
Unio (Plagiola) imbricatus, Morch, Malak. Blatt. vii. p. 205 (1860-61) ’. 
Unio encarpus, Lea, Proc. Acad. Phil. 1868, p.95°; Journ. Acad. Phil. (2) vi. p. 294, t. 42. fig. 105 °; 
Obs. Gen. Unio, xii. p. 54, t. 42. fig. 105 *. 
Hab. E.(?) Nicaragua: probably from San Juan ((rsted '). 
CentraL Nicaraaua: Lake of Nicaragua (Bridges 2~*). 
Since the Table of the species of Unio. was printed, Dr. R. Bergh, of Copenhagen, has 
been kind enough to obtain for me the typical specimen of U. imbricatus, Morch, for 
examination, and I find that it agrees in all its essential characters with U. encarpus, Lea. 
The concentric ridges are minutely waved, especially in the fore part, and this is what 
Lea meant by his expression “ festoon-like strie,” and from which he took the specitic 
name “encarpus.” On the hinder half of the shell in the typical specimen there are 
some impressed lines radiating from the summits to the ventral margin, and crossing 
the concentric ridges at a right angle (see our fig. 6¢); these are not mentioned in 
Lea’s description, but some of them are visible in his figure. We now take the 
opportunity of figuring Morch’s type. 
15. Unio caldwelli. 
Unio caldwelli, Lea, Proc. Acad. Phil, 1858, p.118*; Journ. Acad. Phil. (2) iv. p. 265, t. 43. 
fig. 145°; Obs. Gen. Unio, vii. p. 83, t. 48. fig. 145°; Sowerby, in Reeve’s Conch. Icon. 
xvi., Unio, t. 89. fig. 477 *. 
