STANTON ! THE MARINE CRETACEOUS INVERTEBRATES. 
39 
There are only three specimens belonging to the species in the collec- 
tion and they agree very closely except in size and state of preservation. 
Of the dimensions given below those under I belong to the figured type. 
I 
Diameter 250 mm. 
Umbilicus 53 
Height of aperture 14S 
Breadth of aperture 72 
II 
III 
210 mm. 
300 mm 
45 
zb 62 
1 1 3 
±175 
63 
94 
The comparisons with described species have already been suggested 
in the discussion of the genus. It seems remarkable that no young speci- 
mens of the species were collected and every small ammonite in the col- 
lection has been critically examined in the hope of finding the sculptured 
young of this form. The only one that at all suggests such an immature 
stage is the specimen described beyond as H. tardense , which shows similar 
sculpture in the umbilicus and even at the diameter of 74 mm. begins to 
show the disappearance of the ribs, especially on the venter and the umbil- 
ical wall, but the umbilicus is relatively broader and the sculpture seems 
too pronounced to permit its reference to this species. 
Locality and position . — “Mouth of canon four miles east of Lake Pueyr- 
rydon ; Ammonite (Belgrano) beds.” 
Hatchericeras argentinense sp. nov. 
PI. IX, Figs. 2-5. 
Shell of about the same form and proportions as H. patagonense but 
probably not attaining so great a size, the flattened band between the 
umbilicus and the middle of the whorl somewhat more distinct than in 
that species ; venter regularly rounded, and smooth on mature whorls ; 
umbilicus funnelform, nearly one-fourth the diameter of the shell, with 
rather narrowly rounded or subangular shoulder and smooth walls on 
adult whorls, but showing distinct, closely arranged ribs in the earlier 
stages ; surface marked by rather prominent, closely arranged ribs, part of 
which begin in the umbilicus of young shells up to a diameter of 50 mm., 
but on later whorls originate on the umbilical shoulder, cross the sides in 
a gentle sigmoid curve and become swollen but not distinctly tuberculate 
near the rounded venter, where they are interrupted by a smooth band, 
