THE NAUTILUS. 



Vol. XXXIV JANUARY, 1921. No. 3 



ANCYLUS OBSCURUS HALDEMAN AND SPECIES REFERRED TO IT. 



BY BRYANT WALKER. 



( Continued. ) 



Through the courtesy of M. Menard of the Museum of 

 Geneva, Switzerland, I have received photographs and other 

 valuable data in regard to the types of the unfigured West-In- 

 dian species of Ancylus described by Bourguignat and have con- 

 sequently been enabled to differentiate the following species 

 with more certainty that I otherwise should have been. 



IV. 



Ferrissia jamaicensis n. sp. PI. Ill, figs. 1-3. 



Shell depressed, oval, slightly wider at the anterior end; 

 lateral margins equally curved; anterior slope nearly straight, 

 being very slightly convex towards the apex; posterior slope 

 concave; the left lateral slope a little convex; the right lateral 

 slope concave; apex obtuse, excentric, turned toward the right 

 side, obscurely radiately striate, situated about halfway between 

 the median line and the right margin and at about two-fifths 

 of the length from the posterior end; lines of growth fine, but 

 distinct and regular, with traces of subobsolete wrinkles on the 

 anterior slope; light horn color. 



Length (type) 5.25: width 3.5, alt. 1.5 mm. 



Length (paratype, Adams' Coll.) 5.1; width 3.25, alt. 1.3 mm. 



Type locality Jamaica. Also Kingston, Jamaica. 



Type No. 34825 Walker Coll. Paratype in Adams' Collec- 

 tion. 



