432 NOTES ON FLORIDA UNIONIDA—SIMPSON. 
parallel with the dorsal line toward the posterior ventral region. Sev-— 
eral of the species are strongly humped, especially in old specimens, and 
by the thickening of the substance of the shell and its growth at the 
ventral posterior point, become very ponderous and somewhat triangu- 
lar in outline. 
Unio subeibbosus Lea. 
(Plate Lxx11l, Fig. 5.) 
Unio subgibbosus Lea. Obs. VI, p. 53, Pl. vi, Fig. 36, June 23, 1857. Oostanaula and 
Etowah rivers, Ga. Rev. G. White. 
A single undoubted specimen, a female of this species, is before me, 
belonging to Mrs, George Andrews, collected by Rugel in Lake Mon- 
roe. The species is close to gibbosus on the one hand and luridus on 
the other. It is less wide and smaller than the former and not so 
pointed posteriorly, and more inflated than the latter. I think it prob- 
able that it is only a small southern race of gibbosus, as the latter has a 
wide distribution and has been found at Columbus, Miss., Claiborne, 
Ala., and other points in the Gulf drainage. 
Unio subluridus, n. s. 
(Plate LxxiJ, Figs. 3, 4.) 
Shell small, elliptical, somewhat narrow and rounded before, with a 
slight tendency to biangulation behind; valves somewhat thin, slightly 
inflated; epidermis striated, rather roughened and shining, yellowish 
chestnut, lighter at the beaks, without rays; cardinal teeth not large, 
subcompressed, double in the left valve, single in the right; laterals 
slightly curved, roughened, not heavy or greatly elevated; anterior 
cicatrices well impressed; nacre coppery and slightly iridescent. Di- 
ameter .55, length .85, breadth 1.50 inches. Locality, Orange Springs, 
Volusia County. ©. W. Johnson. 
Three shells of this little form are before me, and while they do not 
possess any very striking characters, yet I find it absolutely impossible 
to refer them to any described species, and, in fact, I hardly know in 
what group to place them. I had considered this a rather thin form of 
U. luridus, but it differs from that species in having much less solid 
teeth and more elevated cardinals, in the color of the epidermis and 
nacre, and in being a less solid shell. It bears some resemblance to 
forms of U. tetricus, but is not so wide, and is a much more evenly 
elliptical shell. There are traces of the furrows in the nacre which I 
have mentioned in connection with this group, and these with the 
rather heavy isolated laterals, as well as a slight resemblance to U. 
luridus (Plate Lxx11, Figs. 1, 2), incline me to place it here.* 
. e,e ~ 2 e . | 
“Since writing the above further study induces me to believe that this species | 
groups with Unio camptodon. 
