422 The American Naturalist. [May, 
But Phillip's term Macrocheilus was preoccupied by Hope, 
in 1838, for a genus of insects and therefore becomes unavail- 
able. Conrad, in 1842, proposed Plectostylus for a group of 
fossil gastropods which evidently belonged to Macrocheilus ; 
but this name also had been used by Beck five years before. 
In i860, Meek and Worthen founded the genus Soleniscus, for 
certain paleozoic shells which now appear to be very closely 
related to the type of Macrocheilus. Inasmuch as the latter 
term had been previously used, Bayle, in 1879, substituted the 
name Duncania, which he subsequently' changed to Macro- 
chilina. The generic title Soleniscus therefore takes precedence 
for the Macrocheilus group, typified by Bncciniiui acntuni Sow., 
and S. typicns M. and W., the synonymy being as follows: 
1841. Macrocheilus Phillips. Palce. Foss. Corn., p. 103. {non Hope, 1838, 
(«^« Beck, 1837). 
P-467.' 
1879. Duncania Bayle. Jour, de Conchyliologie, Vol. xix., p. 35. 
1880. Macrochilina Bayle. Ibid., Vol. xx., p. 241 . 
If the assumed differences in certain characters of the De- 
vonic and earlier Carboniferous species described under Ma- 
crocheilus are real, and are of sufficient import to separate gen- 
erically this group from Soleniscus, as has been suggested, 
some other generic term must be employed to designate the 
group. In this case, Bayle's name Macrochilina might easily 
be made to answer; but it is very doubtful whether this 
would be expedient. A more advisable plan would be to trans- 
fer to other genera the several species described under Ma- 
crocheilus, but which perhaps do not properly belong there. 
In this way it is thought that Soleniscus will form naturally a 
very compact and easily distinguishable group, at least in so 
far as the American species are concerned, and apparently also 
the European. 
Soleniscus consequently embraces paleozoic gastropods 
■ Jour, de Conchyliologie, (3), Vol. xx., p. 241. 1880. 
