198 MANUAL OF THE MOLLUSCA. 
Distribution, about 700 species. Trias—Chalk. Coast of 
Chili (D’Orbigny), Santa Fé de Bogota (Hopkins), New Jersey, 
Europe, South India, and New Zealand. 
In this, as in almost every case, the figures represent the 
number of species which haye been described, and which gene- 
rally pass current as species. It is very probable that when all 
the forms have been thoroughly examined many may turn out 
to be nothing more than variations of the same species, due to 
differences of age, &c. Thus, according to Mr. Seeley, the Am- 
monites splendens from the greensand of Cambridge, comprises 
not only the form so-named, but fourteen others occurring in 
the same bed, and which have received distinctive specific names; 
A. planulatus is made up of five so-called species. Looked at 
from this point of yiew the 700 would be replaced by a much 
smaller number. 
Captain Alexander Gerard discovered ammonites similar to 
our L. oolitic species, in the high passes of the Himalaya, 16,200 
feet above the sea. 
Section A. Back with an entire keel. 
1. Arietes, L. oolites, A. bifrons (Pl. III., Fig. 6), bisul- 
catus (Pl. ITI., Fig. 7). 
2. Falcifert, L. oolites, A. serpentinus, radians, hecticus. 
3. Cristati, cretaceous, A. cristatus, rostratus (Fig. 62), 
varians. 
B. Back crenated. 
4, Amalthet, ool. A.amaltheus, cordatus, excayatus. 
5. Rothomagenses, cret. A. rothomagensis, from othoma- 
gum, Rouen (PI. IIT., Fig. 4). 
C. Back sharp. 
6. Disci, oolitic, A. discus, clypeiformis. 
D. Back channelled. 
" Dentatt cret. A. dentatus, lautus. 
fee ae A. Parkinsoni, anguliferus. 
E. Back squared. 
8. Armat, L. ool. A. armatus, athletus, perarmatus. 
9. Capricorni, _ LL. ool. A. capricornus, planicostatus. 
10. Ornati, ool, A. Duncani, spinosus (Pl. IUI., 
Fig. 5). 
d 
