PYCN ODONTIDiE. 
223 
teeth. Vertebral axis at origin of dorsal fin midway between the 
dorsal and ventral borders of the fish. Dorsal fin with more than 
50 rays, occupying considerably more than half of the back, much 
more elevated than the anal fin, which has 45 rays, and the length 
of which equals about three-quarters that of the dorsal. Ridge- 
scales coarsely serrated; flank-scales delicate, marked with feeble 
rugae, which are mostly transverse. 
A small fish in the Palaeontological Museum, Munich, not 
improbably young of this species, is named Microdon nanus , A. 
Wagner, Joe. eit. vol. ix. (1362) p, 344. 
Form. 6f Log. Lower Kimmeridgian (Lithographic Stone) : Bavaria. 
37369. Plaster cast of type specimen ; Kelheim. Purchased , 1863. 
P. 1625, P. 3764. Pine large specimen partly in counterpart, 
showing remains of the pelvic fins ; Solenhofen. 
Egerton and Enniskillen Colls. 
P. 1631. Caudal region, with nearly complete caudal fin ; Kelheim. 
Egerton Cold. 
P.3765. Imperfect caudal fin ; Kelheim. Enniskillen Coll. 
Microdon radiatus, Agassiz. 
1839-44. Microdon radiatus , L. Agassiz, Poiss. Foss. vol. ii. pt. ii. 
p. 208, pi. lxix. c. figs. ^ 7 /17a 2 
1840. Microdon radiatus , R 
.. * 
. Owen, 
7 J. i*7o 7 **<*}*< 
Odontography, p. 73, pi. xliii. fig. 1. 
Type. Imperfect fishes. /aS^- 
A much smaller species than the type, nearly similar in general 
form and proportions, but with relatively deeper abdominal region. 
Principal series of splenial teeth wider than the two outer series, 
of which the outermost is considerably the largest. Ridge-scales 
with three or four coarse serrations, of which the hindermost 
is a large denticle; flank-scales robust, marked with prominent 
rugae which are mostly transverse and radiating. 
The laminar expansions on the neural and haemal arches are 
well shown in several specimens recorded below, proving that their 
absence in the original fossils examined by Agassiz was accidental. 
The neural spines are remarkably robust in the abdominal region. 
Form. <$f Log. Purbeckian : Dorsetshire. 
All the following specimens were obtained from the neighbour¬ 
hood of Swanage:— 
19013. Fish 0*105 in length, wanting the pelvic fins and the 
greater part of the dorsal and anal fins. Purchased , 1844. 
