608 PBOCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



except the rounded wing of the females covered with pustules; beaks 

 rather low, incurved and turned forward over the well-developed 

 lunule, which is elongated and filled with epidermal matter; beak 

 sculpture strong, consisting of irregular, subparallel ridges which are 

 curved upward behind, and fine radiating ridges in front of and behind 

 this; epidermis dark olive; hinge plate rather narrow; pseudocardi- 

 nals strong , ragged ; laterals long and straight, near to the pseudocar- 

 dinals; adductor scars shallow; cavity of the beaks rather deep and 

 compressed, female shell more compressed than that of the male. 



Animal with the inner gills much larger than the outer, generally free 

 for the most part from the abdominal sac; palpi enormous, elongated, 

 united to each other behind, and to the mantle a part of their length; 

 mantle thin, with a thickened, dark, double border, the inner edge often 

 toothed throughout, the base much thickened at the posterior end and 

 folded at the branchial opening; branchial opening large, with numer- 

 ous crowded papillse; anal opening smooth or with only fine denticula- 

 tions; superanal opening long, closed below; in the female there is a 

 thickened flap of the mantle which fills the circular posterior expansion 

 of the shell, and which has a smaller flap inside; foot and abdominal 

 sac large, the latter winged in front.^ 



fTRITOGONIA TUBERCULATA Barnes. 



* Unio tuherculatus Barnes, Am. Jl. Sci., VI, 1823, p. 125, pi. vii, figs. 8a Sb:^ — *HiL- 



DRETH, Am. Jl. Sci., XIV, 1828, p. 282. — Short and Eaton, Transylvania JL, 

 1831, p. 76.— *Eeeve, Conch. Syst., 1, 1841, p. 118, pi. lxxxviii, fig. 5,—* Han- 

 ley, Test. Moll., 1842, p. 182; *Biv. Shells, 1843, p. 182, pi. xx, fig. 27.— *Potiez 

 and MiCHAUD, Gall. Moll., 1844, p. 158, pi. Lx, fig. 1. — *Catlow and Eeeve, 

 Conch. Nom., 1845, p. 64. — * Reeve, Elements of Conch., 1860, II, pi. xxxiii, 

 fig. 183.— * Calkins, Pr. Ottawa Acad. Sci., 1874, p. 45.— *B. H. Wright, 

 Check List, 1888.— * P^tel, Conch. Sam , III, 1890, p. 170. 



* Margarita {Unio) tuherculatus Lea, Syn., 1836, p. 17; 1838, p. 16. 



* Margaron ( Unio) tuherculatus Lea, 1852, p. 23 ; 1870, p. 34. "^ 



* Mxja tuherculata Eaton, Zool. Text-Book, 1826, p. 217. 



* Unio pustulata Swainson, Treat, on Mai., 1840, p. 271, fig. 54^. 



'^ Unio gigas Sowerby,^ Conch. Icon., XVI, 1867, pi. lvi, fig. 287. 



^ I have never seen a specimen among the hundreds examined that had young or 

 ova in the gills. But I have seen spermatozoa in specimens with inflated shells and 

 ova in those with the wing. Mr. H. M. Kelly, of Mount Vernon, Iowa, who has made 

 a very careful study of the anatomy of many of our Unionidse, assures me that the 

 form with the compressed shell, having the expanded flap behind, is the female. 



"It has been claimed that this species was previously described under the name of 

 Obliquaria verrucosa by Eafinesque, but I am unable to make anything out of his 

 figure or description; hence I use the name given by Barnes. Barnes's name was 

 used by Eafinesque for the species which the former called Unio verrucosus, but as 

 Eafinesque placed his species in Obliquaria, and as the generic names of both forms 

 are changed in this work, I do not consider Barnes's name preoccupied. 



^I think that this is a large, rather high male of the species in question. I can not 

 find any description of Unio gigas by Swainson, to whom Sowerby credits this species, 

 and the Megadomus gigas of Swainson (which, so far as I know, is undescribed) can 

 not be it, as the latter says that his genus, Megadomus, has the lateral teeth imperfect, 

 one or none. Treatise on Mai., p. 266. 



