228 
ACTIN 0PTERYG1I. 
1852. Pycnodus hugii,P. A. Quenstedt, Handb. Petrefakt. p. 213, pi. xvi. 
fig. 10. 
1856. Mioj'odon hugii, J. J. Heckel, Denkschr. k. Akad. Wiss., math.- 
naturw. Cl. vol. xi. p. 201. 
(F) 1858. Pyhnodus hugii, F. A. Quenstedt, Der Jura, p. 781, pi. xcvi. 
figs. 30, 31. 
1860. Pycnodus hugii, F. J. Pictet, Kept. & Poiss. Foss. Jura Neu- 
chatelois, p. 56, pi. xiii. figs. 4-8, pi. xix. fig. 2. 
(?) 1860. Pycnodus notabilis, F. J. Pictet (? errore ), ibid. p. 58, pi. xiv. 
fig. 1. 
1864. Pycnodus irregularis, H. Credner (errore), Zeitsclir. deutscli. 
geol. Ges. vol. xvi. p. 244, pi. xi. fig, 5. 
1875. Microdon hugii, K. Fricke, Palseontogr. vol. xxii. p. 371, pi. xx. 
figs. 10-16. 
1880. Microdon hugii, C. Struckmann, Wealdenbild. Hannover, p. 90, 
pi. iii. fig. 8. 
Type. Portions of mandibular dentition; Soleure Museum. 
A large species, known only by the dentition. Yomerine denti¬ 
tion [according to Fricke] very narrow, and the teeth of the median 
and inner paired series widely spaced; median teeth of irregularly 
rounded form, scarcely broader than long ; those of the inner paired 
series irregularly triangular or quadrangular, antero-posteriorly 
elongated; those of the outer paired series narrowest and much 
elongated antero-posteriorly. Splenial teeth closely arranged; 
those of the principal series about twice as broad as long and more 
or less truncated at their outer end ; those of the innermost series 
and of the inner flanking series relatively small and about equal in 
size; those of the outermost series larger than the latter, though 
less than half as large as the principal teeth, slightly elongated 
transversely and truncated at the inner end. 
The largest known splenial dentition measures about 0*05 in 
length, and the irregular subdivision of some of the teeth is 
frequently observed. 
Form, df Log. Corallian and Kimmeridgian: Hanover, Yuirtem- 
berg, an Switzerland. Portlandian : Hanover ; (?) also S. England. 
Purbeckian: Hanover. {/, }Y) /caVu^cv/- 
P.1654 a, b. Left splenial dentition, somewhat broken, and another 
abnormal fragmentary specimen ; Kimmeridgian, Soleure, 
Switzerland. Egerton Coll. 
P. 7443. Left splenial; Kimmeridgian, Sohlewerke, Hanover. 
Purchased, 1895. 
P. 2297. Imperfect small left splenial dentition ; Portlandian, 
Hanover. Presented by Mrs. Burton , 1882. 
