56 SYSTEMATIC ARRANGEMENT 



B. Tsenioglossa. Teeth in seven longitudinal series, 3 - l"3. Ten- 

 tacles cylindrical (p. 54). 



Fam. XXIII. CERITHIOPSID^. 



Eyes on the upper inner base of the tentacles. Tentacles close 



together in front, cylindrical. Proboscis 1 Foot elongate, 



much produced and double-edged in front, tapering behind. " Teeth 

 3 • 1 • 3 ; central large, bifid ; lateral linear." — Alder, MSS. Oper- 

 culum annular, nucleus apical. 



1. Cerithiopsis. 



Shell turrited ; mouth ovate ; canal short, open, rather bent up. 

 Operculum ovate, triangular, apex acute. — Adams, t. 25. f. 5 a. 



1. C. tubercularis, Forbes fy Hanley, B M. t. O.O. f. 1, 2 ; Adams, 

 Gen. Moll. t. 25. f. 5. 



Head rather broad and short, flanked by two obtusely subulate 

 tentacles, widening slightly at their bases, with more slender flat 

 tips. Eyes rather close together, towards the centre of the tentacle- 

 base. Mouth inferior, furnished with a retractile proboscis. Tongue 

 armed with teeth, which appear to resemble in their arrangement those 

 of Trichotropis. Mantle not reflected, furnished with a rudimentary 

 siphonal fold (not extended beyond the shell). Foot oblong, sub- 

 quadrate in front, where it is furnished superiorly with a mentum, 

 obtuse behind, grooved for half its length below, the groove termi- 

 nating in a perforation. Operculigerous lobe well developed. Oper- 

 culum corneous, of concentric elements ; nucleus terminal. Shell 

 like Cerithium. 



Teeth of Cerithiopsis tubercularis 3 • 1 • 3, in seventy cross rows ; 

 central tooth broad, ovate, with two small divergent apical teeth ; 

 lateral all similar, elongate, hooked at the tip. Operculum oblong, 

 rather more angular at the hinder end ; subannular nucleus small, 

 on the front inner side. 



The foot of Cerithiopsis is usually carried in advance of the ten- 

 tacles ; there is a distinct margined operculigerous lobe without 

 wings or caudal appendages. 



The Cerithiopsis inhabits quiet sheltered pools on the shores 

 among the minor Algse, and it is very lively. There can scarcely be 

 a greater contrast than between it and Cerithium reticulatum, which 

 has the entire aspect of an elongated Rissoa, whereas this is an un- 

 doubted Canalifer, with evident relations to Eulima and Chemnitzia. 

 —Clark, 492. 



Mr. Stimpson, from the examination of the animal, refers Ceri- 

 thium terebrale and C. Emersonii, Gould, to the genus Cerithiopsis. 

 — Stimpson, Test. N. Eng. 45. 



Mr. Forbes refers this genus to the family Cancellariadce with 

 Trichotropis.— Brit. Moll. ii. 3G4. 



