Ih ite PSEUDOCERATITES OF THE CRETACEOUS. 
MEroIcocERAs SwaALLoyi (Shumard). 
Jel DO thes, (ee Tea GOR, sires tl Ps JRL DE ategsy Te 
Ammonites swallovi Shumard, 1859, Trans. St. Louis Acad. Sci., Vol. I, p. 591. 
So far as I have been able to see, this species has not been previously 
figured, but that described below as whitei has been the one selected as the 
typical form of swallovi. 
The following quotation from Shumard’s description shows that while 
he had in hand perhaps both of the species here described his remarks seem 
to apply more decidedly to the one selected as swallovi rather than to its less 
-prominently nodose and more complex companion. Shumard states “dorsum 
[venter] flattened, transversely ribbed, nodose-bicarmate; * * * umbili- 
cus deep, exhibiting about one-third of each of the inner volutions and about 
as wide as one-half of the width of the last volution.” If he had in hand such 
a specimen as the one he mentions as being 6 inches in diameter, and it was 
a representative of whitei, this large umbilicus would be just about in this 
proportion, but it would be inapplicable to an ephebic stage as a young 
specimen of this species. If he had had a specimen of M. swallovi, the 
large umbilicus would have been found in the neanic and ephebic stages in 
about this proportion. Shumard’s other remarks apply also about equally 
well to either species, but the sutures, as described by him, point out quite 
clearly the typical form. ‘Dorsal saddle almost double the width of the 
superior lateral lobe and divided into two unequal branches by a short 
subconical auxiliary lobe; the dorsal [outer] branch having three small 
notches, while the inner one is rounded and has usually only a single small 
notch at its internal border.” Such simple outlines as these occur only in 
the forms here referred to as swallovi, and one of the specimens (Pl. XIII, 
fig. 2) came from Grayson County, Tex., the typical locality quoted by 
Shumard. 
The young figured (Pl. XI, figs. 7-15) and the sutures (Pl. XJ, figs. 
18-23) were taken from a specimen found in a piece of the matrix cracked 
off from the specimen shown in fig. 16 and are quite likely the young of 
this species, but it is probable that at this age the differences are slight 
between this species and white7. Three specimens were obtained from this 
piece of matrix. That to which figs. 12, 13 belonged reached an older 
