AMMONlTlDuE. 83 



AcANTHOCERAS, Neumayr, 1815. 



Distr. — 36 sp. A. Rotomagense^ Brong. (xxxv, 10). 



Shell with a moderately wide umbilicus and not veiy elevated 

 whorls. Margin of aperture and length of body-chamber un- 

 known. The sculpture consists of quite straight ribs, which 

 become constantly stronger from the suture outwards to the 

 external side, which are frequently ornamented with a greater or 

 less number of tubercles or nodes, and are most curved in young- 

 individuals. The development of the external side is very vari- 

 able, the middle line sometimes with uninterrupted ribs, some- 

 times with a furrow, sometimes with a line of tubercles, the 

 elements of which attempt to unite into a keel. Lobular line 

 much reduced ; besides the two laterals on the flanks there is at 

 most one auxiliary, or a row of two to three extremel}^ small 

 deep-lying auxiliaries ; bodies of the lobes and saddles plump 

 and broad, the last broader than the first, no branching, but only 

 a dentation of the lobes. Siphonal and first lateral usually not 

 very different in size, the first often larger than the last ; second 

 lateral much smaller than the first, both one-pointed. 



Stoliczkaia, ]S"eumayr, 1815. 



Dedicated to Dr. Stoliczka, of the G-eological Survey of India. 



Distr. — 8 sp. Cretaceous ; India. S. dispar, Stol. (xli, 62, 68). 



Forms allied to Hoplites dutempleanus, with expanded body- 

 chamber, embracing three-fourths (?) of a whorl. Margins of 

 aperture curved, produced at the middle of the flanks, slightly 

 emarginate at the external side. Inner whorls with radial ribs 

 which are not interrupted on the external side, and usually hei'e 

 attain their maximum strength ; body-chamber smooth or with 

 thickened ribs ; external side without keel or furrow. Lobular 

 line branched, consisting of a siphonal, two lateral, and one or 

 more less dependent sutural lobes. 



Hoplites, Neum., 18'75. 



Syn. — Sonneratia, Bayle, 18*78. 



Distr. — 50 sp. Cretaceous, S. Archiacianiis, d''Orh. (xli, 68, 69). 



Derived from the group of forms represented by Perispliinctes 

 involutus, with moderately narrow umbilicus and high whorls ; 

 thickness very variable. Margin of aperture and length of 

 body-chamber unknown. Sculpture consisting of divided and 

 curved ribs, which originate near the umbilicus or in the middle 

 of the flanks in small, thickened, primary ribs or a tubercle ; 

 ribs interrupted on the periphery, often separated by a deep 

 furrow, or at least feebler at this point ; ribs enlarged at both 

 extremities, weaker at the middle of the flanks. Lobular line 

 complicated, with branches and numerous auxiliaries ; lobular 

 bodies not very plump ; saddles as wide or (mostly) wider than 



