206 HIPPURITIDA. 
and the teeth and apophyses so firmly wedged into their respec- 
tive cavities as to suggest the notion that the valves had become 
fixed about a quarter of an inch apart, and ceased to open and 
elose at the will of the animal. 
BIRADIOLITES, d’Orbigny, 1850. Ligamental groove visible in 
one or both valves, sometimes occupying the crest of a ridge, 
and bordered by two similar areas. Fossil, 5 sp. Chalk; 
France. &. canaliculatus (exviii, 38). 
LAPEIROUSIA, Bayle. &. Jouanetti, Desm. 
SYNDONITES, Pirona, 1869. Cardinal teeth grown together 
almost in their entirelength. &. Stoppaniana, Pir. Cret.; Friaul. 
SPHAHRULITES, de la Merthe, 1805. (Acardo, Brug. Jodamia, 
Defrance. Birostrites, Lam.  Dipilidia and Agria, Math. 
Heterocaprina, Munier-Chalmas.) Attached valve generally 
elongately conical with longitudinal, more or less foliated surface 
and the margins radiately ribbed internally with a single umbonal 
rib extending the whole length of the valve. Free valve smaller, 
similar in form and structure to that of Radiolites, but with a 
median tooth or columella corresponding to the hinge-rib of the 
other valve, in which there is on each side of the rib a cartilage- 
process, the two cartilage-plates being sometimes united in 
front, and next to them are situated the raised muscular scars. 
Te unisulcatus, Matheron (exviii, 39). 
The presence of a hinge-rib readily distinguishes the present 
group from Radiolites restricted), and the absence of any other 
ribs or folds in the BPW valve separates it from Hippurites. 
TamiosoMa, Conrad, 1856. 
The type of this genus is a very peculiar fossil from the upper 
miocene deposits of California, 7. gregaria,Conn. Gabb, in the 
second volume of the Paleontology of California (pp. 61-63), 
has very ably discussed the organization of this fossil, and 
comes to the conclusion that it is most likely a species of the 
Hippuritide. The specimens which have, up to the present, 
been found, resemble the elongated, lower valve of Hippurites 
with a small place of attachment apparently at the thinner or 
lower end. They are subcylindrical with rather thick walls con- 
sisting of two or three layers, possessing the same reticulated 
and striated structure as that of Radiolites, and others. The 
lower portion of the shell is composed of a large number of 
irregular chambers or septa which are produced by lateral pro- 
longations of the inner wall. The end is occupied by a large 
cavity, similar to the ‘“body-chamber” of Hippurites, but no 
impressions of teeth have as yet been observed init. The outer 
surface is longitudinally striated in the type species which grows 
in clusters, as does, for instance, H. organisans, Defr. 
In some respects Tamiosoma recalls the organization of the 
peculiar Hippurite from Jamaica, called by Woodward, Barrettia. 
