184 The American Geolo(/isf. March, i«)7 
cinnati, is cf>nvex and very wide in proportion to the shells 
length. P. (jibbosd is outwardly like small P. prmcosis^ but 
is smaller, thicker proportionately, and generally triangular 
in outline. 
Rhynchonella. 
The species of RhynchoncJln that are found in the Galena 
and Maquoketa series had been practically all referred to one 
.species by paleontologists, but have again been gradually sep- 
arated more or less distinctly in the same manner as the group 
of Ortln's fesfudiiiar/d auct., described in part three of this 
paper, had been. These two groups of fossils are in fact 
similarly composed, both comprising several closely related 
species. In the Orfhis festudinarid group however tlie Ma- 
quoketa species, as known, are the more numerous, while the 
Rhynchotiella group has most representatives in the Galena 
series. It includes the following: — 
1. RhijiichonelUi miiinesotensis Sardeson, Bull. Minn. Acad. 
Nat. Sci., vol. 3, p. 333, pi. 4. f. 21-23, (1892). lihynchotrewa 
ina'quivalois W. & S. (partim) Final rep. Geol. Sur. Minne- 
sota vol. 3, pt. 1, pi. 34, f. 9, 10, 15-23. (not 12-14) : is found 
from the Butf limestone bed (1) to the Stictopora bed (4) in 
this area. 
2. lihyncJiouel/a (tins/iei N. H. Winchell : 14th Ann. Kep. 
Geol. Sur. Minnesota, p. 315, pi. 2, f. 5, 6; Bhynchofrenut 
ainsUei W. & S. Final rep. Geol. Sur. Minn, p- 459, pi. 34, f. 
1-8, (1893) is from the Stictoporella bed (3). 
3. Rhynchonelln iacrebescens'B.wW (partim); Pal. N. York, 
vol. 1, p. 146, pi. 33, fig 13. a.-f. (1847). Rhynchonella incre- 
bescens Billings, Geol. Canada, p. 168, tig. 153(1863) ; Trema- 
tospira quadrvplicafa Miller, Cincinnati, Q. Jour. Sci., vol. 2, 
p. 60, f. 6-7 (1875); Rhynchotrema Incvqiiivalvis W. & S. 
(partim), Final rep., Geo. Sur. Minnesota, vol. 3, pt. 1, p. 459, 
pi. 34, f. 12-14 only (1893).* This species is abundant in the 
Fucoid bed (5) gradually disappearing in the Camarella 
bed (8). 
*Spirifer incequivalvis Castelman, is said by Winchell and Schii- 
chert, loc. cit. to have theprioritjs and to be synonymous but they con- 
fuse two species and do not tell which is Castelnau's. R. mcrebesce)is 
Hall is only technically applicable to this species, R. qimdrnplicata 
is a preoccupied name, hence I have followed Billing's identification, 
R. increfyescens Hall, Bill (1863). 
