6° 38 THE NAUTILUS. 
This differs in its proportions from M. carinulata Desh. to which 
Carpenter referred it. The latter is with little doubt merely a 
young specimen of M. pallida Sby. the M. donaciformis of Gray, 
better known as angulata Gray.  Itis a thinner shell with a sharp 
keel terminating in a somewhat recurved acute point, and having 
the beaks more anterior than Mf. modesta. The beaks are decidedly 
more distant in the latter. 
Mulinia coloradoensis, n. s. (Plate I, upper fig.). 
Shell larger, solid, rude, equilateral, resembling MM. modesta, but 
having the posterior dorsal margin more arched, the base behind 
the posterior dorsal angle, somewhat concavely flexuous, and the 
surface anteriorly and on the dorsal area marked with obsolete, 
little elevated radii. Lon. of a medium sized specimen 49, alt. 36.5, 
diam. 52 mm. 
Habitat, Head of the Gulf of California in the estuary of the Col- 
orado River, abundant; Dr. E. Palmer. 
M. coloradoensis var. acuta, n. s. (Plate I. left fig.). 
Shell thinner, longer, and more flexuous posteriorly. Lon. 40, 
alt. 29 mm. 
Habitat, with the typical form, common. 
Mulinia Bradleyi, n. s. (Plate I, right fig.). 
Shell resembling a miniature M. donaciformis but more com- 
pressed, shorter, the beaks smaller and less prominent, the posterior 
dorsal margin much more arched, no basal flexuosity, the pallial 
sinus longer and more rounded internally, and the epidermis ele- 
vated into narrow fringes, more or less regularly spaced. Lon. 32, 
alt. 26, diam. 15 mm. 
Habitat, Panama; Bradley, in U.S. Nat. Museum. 
TRIODOPSIS + MESODON.—DISTRIBUTION, ETC. 
BY ROBERT E. C. STEARNS. 
In the last number of the Manual (Pulmonata Series), Mr. Pils- 
bry very properly unites Triodopsis and Mesodon ; both of these are 
Rafinesque’s names; in order of date, the former has priority, there- 
fore Mesodon must take a back seat. As to the propriety of these 
names, neither is satisfactory. Triodopsis the name that must stand 
for the reason above given, priority, conveys a false idea, for as 
Mr. Pilsbry says, in the remarks' that precede his list: 
1Manual of Conchology, pt. 34, pp. 74-76. 
