CONCHIFERA. 445 
porous, the pores leading to canals in the outer shell-layer, 
which open round the pallial line upon the inner margin; 
anterior cartilage-pit deep and conical, posterior shallow; 
ambonal cavity turned to the front (uv); teeth 2, straight, sub- 
central, the anterior largest, each supporting a crooked musculzr 
apophysis, the first broad, the hinder prominent, tooth-like ; 
inflections (m, n) surrounded by deep channels. 
H. cornu-vaccinum attains a length of more than a foot, and 
is curved like a cow’s horn; the outer layer separates readily 
from the core, which is furrowed longitudinally. The ligamental 
inflection (/) is very deep and narrow, and the anterior tooth 
farther removed from the side than in H. bi-oculatus and radiosus 
(Figs. 233, 234); the posterior apophysis (a’) does not nearly fill 
the corresponding cavity in the lower vaive. In H. bi-oculatus 
and some other species there is no ligamental ridge inside; 
these, when they have lost their inner layer, present a cylin- 
drical cavity with two parallel ridges, extending down one side. 
The third inflection (n) is possibly a siphonal fold, such as exists 
in the tube of Teredo, and sometimes in the valves of Pholas, 
Clavagella, and the caudate species of Trigonia. 
The development of processes from the upper valve, for the 
SEY Sayyid bases 
SVS oe 
] 
Quy { 
| 
2 
\ | 
| 
\ 
| 
ZZ 
Fig. 237. Longitudinal section ; upper half, 3. Fig. 238. Transverse section, =. 
Hippurites cornu-vaccinum, Bronn. Salzburg, 
l, m. n, duplicatures ; uw, umbonal cavity of left valve; r, of right valve; c, c’, ca> 
tuage-pits: ¢, t’, teeth; z, a’, muscular apophyses; d, outer shell-layer. Fig. 237 is 
taken in fle line @ } of Fig. 238, cutting only the base of the posterior tooth (z'‘). 
Fig. 238 is from a lareer specimen, at about the ievel dd of Fig. 237, cutting the point 
of the posterior apophysis (a'), and showing the peculiar shell-texture deposited by 
the anterior adductor (a). 
attachment of the adductor muscles harmonises with the other 
peculiarities of the Hipeyrite. The equal growth of the margins 
