bg IBERUS. 
from its resemblance in form to a horse’s foot, when held witi: 
the flat anterior dorsal margin downwards. Few shells are 
found to concentrate so many beauties as the Hippopus Ma- 
culatus, commonly called the Bear’s-paw clam; the delicate 
whiteness of the interior, the undulating edge, the radiating 
fluted columns, adorned at intervals with crisped fringes, and 
the richness of the variegated colouring are such as to secure 
the admiration of the most superficial observer. Fig. 156, H.- 
Maculatus. Sowerby has mentioned fossil species. 
HOR'TOLUS. Montf. Sprrotma, Lam. Microscopic. 
HYALAVA. Lam. ( Hyalus, glass.) Fam. Pteropoda, Lam. The- 
cosomata, Bl. Deser. Globose, glassy, transparent, with a tri- 
angular opening at the upper part where the dorsal portion ad- 
vances beyond the ventral; ventral portion vaulted; dorsal 
more flat; lower extremity tridentate. Obs. The singular struc- 
tures composing this genus were formerly taken for bivalves, 
and named Anomia Tricuspidata, &. They are now known to 
belong to the class of molluscous animals, called Pteropeda, 
from the wing-shaped organs of locomotion. A species of 
Hyaleea occurs in Sicily, in a fossil state. Fig. 226, H. Tri- 
dentata. 
HYALINA. Studer. Vrrrina, Drap. 
HY’ ALINE. (Hyalus, glass.) Glassy, thin, transparent. Hw. Cari- 
naria Mediterranea, fig. 488. 
HYDROBRANCHIA'TA. Bl. (Hydra, water; branchie, gills.) 
The first section of the order Gasteropoda, Lam. containing 
Molluscs which breath water only; divided into the families 
Tritoniana, Phyllidiana, Semi-phyllidiana, Calyptracea, Bul- 
leana, and Aplysiana. 
HY’RIA. Lam. A genus composed of species of Nayades, distin- 
guished by their alated dorsal margins, and lamellated lateral 
ee Hyria Corrugata, fig. 143. Hyria Syrmatophora, 
r. 144, 
JANERA. Schum. A genus composed of species of Pecten, 
Auct. having oblique plicee or callion each side of the ligamen- 
tary pit. 
JAN’THINA. Lam. (Janthum, a violet.) Fam. Neritacea, Lam. 
Oxystomata, Bl. Deser. Sub-globose, thin, fragile, spire short, 
consisting of few whorls; aperture angulated, at the anterior 
junction of the inner and outer lips; columella tortuous, con- 
tiguous to the axis; outer lip thin, sinuated in the centre. Obs. 
The shells composing this genus are celebrated for their beau- 
tiful purple colour. The animal possesses a curious vesicular 
process, which keeps it floating on the surface of the water; it 
exudes a purple secretion when irritated. Fig. 333, J. Fragilis- 
JATARO'NUS. Adanson. Cxama, Auct. 
VBERUS. Montf. Carocoiua, Lam. 
