40 
CHjDI JEROIDEI « 
The following species are placed here :—- 
Palceomylus crassus : Rhynchodus crassus, J. S. Newberry, Eep. 
Geol. Surv. Ohio, vol. i. pt. ii. (1873), p. 312, pi. xxix. 
fig. 3, and Palseoz. Fishes N. America (1 889), p. 49, pi. 
xxviii. fig. 4.—Corniferous Limestone ; Ohio. [Columbia 
College, New York.] 
Palceomylus frangens : Rhynchodus frangens , J. S. Newberry, 
op. cit. (1873), p. 311, pi. xxviii. figs. 2, 3, and op. tit. 
(1889), p. 48, pi. xxix. figs. 2, 3.—Corniferous Limestone; 
Ohio. [Columbia College.] 
Palceomylus greenei : Rhynchodus greenei , J. S. Newberry, op. cit. 
(1889), p. 51.—Hamilton Group; Milwaukee, V isconsin. 
r/9-y^cL\ r< >*7 ' 
7>'*f - 37 > ^ pi-if ■ 
Family SQUALORAIIDiE. 
Body depressed, but elongated. Head produced into a flat ros¬ 
trum, without lateral teeth. Dentition consisting of thin, trans¬ 
versely curved plates, without differentiated tritoral areas ; a single 
pair in the lower jaw, meeting at the symphysis, and two pairs in 
the upper jaw, the hinder pair being closely apposed in the median 
line anteriorly, but divergent posteriorly. Dorsal fin-spine absent. 
Males with a prehensile spine upon the snout. 
Genus SQUALOR A JA 5 Riley. 
[Proc. Geol. Soc. vol. i. 1833, p. 484.] 
Syn. Spinacorhinus, L. Agassiz, Poiss. Foss., Feuill. 1837, p. 94. 
Rostrum much produced ; tail gradually tapering to a point. 
[Median fins unknown.] Teeth marked with a series of hard, 
parallel, longitudinal corrugations ; rostral spine of male slender and 
pointed, with expanded base and a cluster of large recurved denticles 
on the inferior aspect near its insertion ; dermal tubercles conical, 
radiately sculptured, sparsely arranged. Vertebral rings well cal¬ 
cified, consisting of several concentric lamellae. 
This genus has hitherto been regarded as a Selachian, though the 
Chimaeroid resemblance of its rostral region, the supports of its lateral 
line, &c., have been pointed out by W. Davies and the present 
writer. The skulls recorded below have a hyostylic appearance ; 
but the writer is indebted to Dr. R. H. Traquair for the information 
that the Edinburgh Museum acquired a specimen some years ago 
proving the arrangement to be truly autostylic, while a pair of 
vomerine teeth occurs in advance of the well-known large dental 
