
654 THE AMERICAN NATURALIST.  [Vou. XXXVI. 
for which is after a long period of oblivion finally secured to 
him. The actual specimen, whose description follows, appears 
to have dropped out of sight altogether ; but if still in existence, 
the present account may perhaps lead to its resurrection. 
Other interesting observations of St. John with reference to 
Edestus and Cochliodus are contained in the form of a personal 
letter to Professor Agassiz, written in 1871, extracts from 
which are quoted in the following, and his sketch of Edestus 
minor is here reproduced. Detached segments of Æ. heiurichi 
have been figured by Newberry! and Trautschold,* and a cor- 
responding example of E. minor from the vicinity of Moscow 
is described by Karpinsky,® but St. John's specimens are the 
only ones, so far as the writer is aware, that have been found 
of the latter species in this country. 
Professor Agassiz was one of the first to pronounce upon the 
nature of these problematical fossils, and compared them with 
the rostral prolongation of Pristis. Leidy saw in their seg- 
mented condition a resemblance to the compound maxillary of 
Lepidosteus, but later regarded them as elasmobranch spines, 
an opinion concurred in by Sir Richard Owen, Newberry, 
Woodward, and most modern writers. They are now definitely 
determined, however, to be the symphysial dentition of cestra- 
ciont sharks.* 
I. ON THE OcCURRENCE OF DINICHTHYS IN THE HAMILTON 
LIMESTONE OF ILLINOIS. 
(August, 1882.) 
* Professor A. H. Worthen has obtained from the Devonian 
limestone of Andalusia, Rock Island County, Illinois, a nearly 
perfect example of the right mandibular dental plate of a small 
species of Dinichthys, which is quite distinct from either of the 
two forms already described by Dr. Newberry from the Ohio 
l Ann. N. Y. Acad. Sci, vol. iv (1888), PI. v Vu 2a, 26; Monogr. U. 5. 
Geol. Surv., vol. xvi (1889), Pl. XXXIX, Figs. 2 
Ha Soc. Imp. Nat. Moscou, vol. lviii (383, fs v Figs. 
3 Verh. b. russ. pee Ges. St. Pétersbourg [2], vol. xxxvi dre pP- 381, 
450, Text-figs. 1c, 
* Geol. Mag. an ix, p. 148; Bull. Mus. Comp. Zoöl., vol. xxxix (1902), No- 3- 
