TRACHELIPODA. 83 



an umber-brown back, and white inside. Inhabits the coasts j 

 of Peru. 



Genus 18 MONOCEROS Lamarck. 



Generic Character. — Shell ovate ; aperture longitudinal, 

 obliquely emarginate at the base ; a conical tooth at the 

 base of the outer lip. 



Monoceros cingulatum. — THB Banded Monoceros. Plate 

 XL fig. 18. Ovato-oblong, with raised spiral bands, and 

 very minutely striated ; the bands black ; the whorls angular 

 above ; the aperture pure white. Inhabits the western 

 coasts of Mexico. 



Genus 19 PURPURA Lamarck. 



Generic Character. — Shell ovate, either smooth, or tuber- 

 cular, or angular ; aperture dilated, emarginate at the base, 

 having a subcaniculate oblique sinus ; columella depressed, 

 ending below in a point. 



Purpura Persica — The Persian Purpura. Plate XL 

 fig. 19. Transversely sulcate, and striated between the 

 ridges ; dark -burnt-umber brown ; ridges cream-yellow, with 

 distant spots of very dark umber brown ; upper ridge and 

 the superior edges of the volutions mucronate ; inside sul- 

 cated and striated, white with yellow lines, the lip black. 

 Inhabits the Indian seas. 



Genus 20— RICINULA Lamarck. 



Generic Character. — Shell ovate, usually tubercular or 

 spinous externally; aperture longitudinal, furnished with a 

 short recurvate canal, terminated by an oblique notch; colu- 

 mella with unequal teeth ; the teeth on the interior of the 

 right lip frequently narrowing the aperture. 



Ricinula horrida. — The Rugged Ricinula. Plate XL 

 fig. 20. External surface covered with strong, obtuse, black 

 tubercles, the interstices being white and transversely stri- 

 ated ; inside of both lips of a rich purple ; outer lip with 



