Geology and Paleontology. 731 
tenuirostris and its allies are the forms most nearly allied to Mixo- 
saurus Baur, and J. tenuirostris has only four digits. From this 
Mr. Lydekker agrees with Dr. Baur that the Ichthyosaurs have 
descended from a tetradactylate ancestor. Two additional species, 
. cantabrigensis and I. conybeari, are described, the former from the 
Greensand of Cambridge (Eng.), the latter from the Lower Lias. 
“The Insect-world of the Lithographic Shales of Bavaria” is 
the title of an extended article in Volume 34 of Paleontographica, 
by P. Oppenheim. Among the fossils described are Cyrtophyllites 
rogeri, a new genus and species of Locustide, two new species of 
Ephemera, Prolystra lithographica, Eucicada microcephala, Ischy- 
opteron suprajurense, n. gen. et sp.; Halometra, a new genus of 
Hydrometride, with two species; three species of Carabide, a 
Prodytiscus, two forms of Lamellicornia, two of Clavicornia, three 
of Sternoxia, one of Rhynchophora, and three of Chrysomelide. 
Creracreous.—A. S. Woodward (P. Z. 8., X. Feb. 21, 1888) 
shows that the lateral line of Scyllium sahelalme, from the chalk of 
t. Lebanon, was supported by a series of half-rings, exactly like 
those met with in Squaloraja and the Chimeroids. The canal of 
the lateral line was ss presumably an open groove; a condition 
which obtains in only two living Selachians, Echinorhinus and 
Chlamydoselachus. 
Squatina eranei is the name given by Mr. S. Woodward to a 
species of “angel-fish” discovered in the chalk of England, and 
distinguishable from the species of Squatina already satisfactorily 
nown by the great relative size of the spinous dermal tubercles. 
No defences of this kind have been found in extinct forms, and the 
ne species has them much smaller in proportion to the size of 
e fish. 
The same geologist also describes certain specimens of mandibles 
of the singular Belonostomus cinctus, revealing the precise character 
of the dentition, and the relations of the bones. The two rami 
occupy only half the entire length of the jaw, the anterior half 
being formed by the enormously elongated pre-symphysial bone. 
The narrow and deep rami meet at a very acute angle; the sym- 
physis is elongate, gradually diminishing to a thin edge below, and 
the large pre-symphysial bone, which is a median unpaired element 
is articulated to the sloping triangular surface thus formed. On the 
latter bone there is a median row of about thirty large conical teeth, 
while a great number of smaller similar teeth—the largest little 
more than one-sixth the height of the largest of the median series— 
are placed irregularly upon the lateral margins of the bone. 
