NO. 3 BELLEROPHONT GASTROPODS KNIGHT 3 



name would be submerged in synonymy. However, the genotype of 

 Protoscaevogyra is known from a single specimen so poorly preserved 

 that it is impossible to discover significant characters. It seems likely 

 that Protoscaevogyra was applied to a sinistral example of some 

 species of Pelagiella. Sinistrality seems to be a common variation 

 in some species of that genus. I place it, along with Proeccyliopterus 

 Kobayashi and Parapelagiella Kobayashi, as a subjective junior syn- 

 onym of Pelagiella. It is my opinion that Kobayashi did not have 

 opportunities to investigate thoroughly the shell morphology of 

 Pelagiella and that his supposed genera are not distinct from it. 



Both of the two genera erected here have a superficial resemblance 

 to Pelagiella. In fact, some unknown worker had labelled the types 

 of Chalarostrepsis praecursor in the National Museum as "Pelagiella." 

 But although Pelagiella seems to have a shallow and broad peripheral 

 emargination, it does not have a deep, V-shaped sinus as in Strepso- 

 disciis nor a deep slit as in Chalarostrepsis. Furthermore, Pelagiella 

 has only two whorls or less that expand more rapidly than in those 

 of either. It is, of course, quite asymmetrical and, in the types of 

 the genotype species at least, in a dextral sense. 



Suborder BELLEROPHONTACEA Ulrich and Scofield, 1897 



Family CYRTOLITIDAE Ulrich and Scofield, 1897 



Genus STREPSODISCUS Knight, new genus 



Genotype, Strepsodiscus major Knight, new species. 



Diagnosis. — Discuslike bellerophontiform gastropods with a deep, 

 V-shaped sinus in the anterior lip culminating sharply at the sharp 

 dorsal crest but without a slit. The final whorl is out of contact 

 with the coil and, at least in the only known species, there is a slight, 

 varying degree of asymmetry in the sinistral sense. 



I am placing Strepsodiscus in the Cyrtolitidae because of the sinus 

 culminating at a dorsal carina or "notch keel." The light contacts 

 of the whorls and the rather steep umbilical slopes speak likewise 

 for that assignment. That it is a bellerophont in spite of its slightly 

 sinistral coiling is attested by the essential bilateral symmetry of its 

 coiling, by its anterior V-shaped sinus, and by the traillike posterior 

 margin of the aperture. 



STREPSODISCUS MAJOR Knight, new species 



Plate i, figures la-m 



Description. — A moderately large species, all observed specimens 

 of which are to a greater or less degree asymmetrical in a sinistral 



