42 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



second lateral lobe is out of its normal position, on account of the fact 

 that the draughtsman accidentally passed from the suture he was drawing 

 to the succeeding one at that point.) The single type specimen measures 

 75 mm. in diameter; umbilicus, 19 mm.; height of aperture, 36 mm.; 

 breadth of aperture, 22 mm. 



The species is doubtfully referred to Hatchericeras on account of the 

 general agreement in form and suture with the type of the genus, and 

 the belief that the young of the type species may have had similar sculp- 

 ture, as indicated by the fact that the tubercles or ends of ribs visible in 

 the umbilicus of H. patagonense are very similar in appearance to the 

 umbilical tubercles on the earlier whorls of the present form. The type 

 of sculpture does not differ greatly from that of H. argentinense and the 

 changes in the different stages of growth are in the same directions. The 

 relative size of the umbilicus seems too large and the sculpture too pro- 

 nounced to permit the identification of this specimen as a young individ- 

 ual of H. patagonense. 



Like the preceding species, this form could probably be referred to 

 Hoplites, in the broad sense in which that term has generally been used. 

 It has some superficial resemblance to H. desori Pictet and Campiche, 

 which Behrendsen has reported from the lower Cretaceous of the Argen- 

 tine Republic, but it is more involute than that species, has a more 

 rounded venter, the ribs are relatively coarser and more distant and the 

 umbilical tubercles are not so pronounced. 



Locality and position. From the Ammonite (Belgrano) beds at mouth 

 of caflon, four miles east of Lake Pueyrrydon. 



HATCHERICERAS? PUEYRRYDONENSE sp. nov. 



PI. X, Figs. I and 2. 



Shell small, of the general aspect of H.f tardense, but more involute, 

 the umbilicus measuring not quite one fifth the diameter of the shell ; 

 venter rounded, but showing a tendency to be flattened in earlier stages ; 

 umbilicus with subangular shoulder bearing incipient tubercles that are 

 visible on the inner whorls, the umbilical slope of the last whorl steep 

 and smooth; surface marked by prominent, slightly sinuous ribs that 

 branch near the middle of the flank and usually either branch again, or 

 have interpolated between 'adjacent pairs a shorter branching rib, so that 



