STANTON I THE MARINE CRETACEOUS INVERTEBRATES. 33 



of the spire marked by numerous fine, thread-like, spiral lines, and by 

 rather prominent, slightly curved transverse ribs, with a tendency to form 

 blunt tubercles on the middle of the whorl, giving it a subangular ap- 

 pearance. The transverse ribs nearly or quite disappear from the back 

 of the last whorl when it becomes carinate, and on the front aspect of the 

 shell the sculpture is almost entirely concealed by the callus. 



Height of the largest type specimen, with apex of spire restored, 27 

 mm.; greatest breadth, 21 mm.; breadth of last whorl, exclusive of 

 wing, 1 1 mm. 



In the general form of the aperture, the excessive thickening of the 

 outer lip and the heavy deposits of callus, this little shell resembles some 

 forms of Pugnellus, and in the preliminary examination of this collection 

 it was referred to that genus. Pugnellus manubriatus Gabb, 1 on which 

 the subgenus Gymnarus was based, especially resembles it in the form of 

 the wing-like expansion of the outer lip and in the callus restricted to the 

 front of the shell. On cleaning some specimens of the Patagonian 

 species more thoroughly, however, it was found that the anterior canal is 

 much shorter and straighter than in any species of Pugnellus, that it 

 lacks the well-developed anterior notch or sinus and is not bent inward 

 toward the aperture at the extremity, and the affinities of the species seem 

 to be with Aporrhaidae rather than Strombidae. It is not a typical Apor- 

 rhais. It has many features in common with the recent A. occidentalis 

 Beck, for which Gabb proposed the subgenus Arrhoges, though the heavy 

 callus on the inner lip and spire and the greater development of an 

 anterior canal prevent its reference to that subgenus. The peculiar 

 rounded boss at the lower end of the callus is not duplicated in that posi- 

 tion in any other Aporrhaid species known to me. 



Locality and position. Abundant in the Ammonite (Belgrano) beds, ten 

 miles east of Lake Pueyrrydon. Represented in the collection by over 

 30 individuals, most of which are very imperfect. 



APORRHAIS (?) sp. 



A larger species, apparently belonging to the Aporrhaidae, is represented 

 by a single specimen consisting of four whorls of the spire from the locality 

 four miles east of Lake Pueyrrydon. The whorls are convex and each 



1 Palaeont. of California, Vol. I, p. 125, pi. 29, fig. 229. 



