19 



1. acuta, Qaoy. 



2. antiquata, Linn. 



3. ausiralis, Q/ioy. 



4. barbata, Soto. 



5. conica, Schum. 



Species. 



6. foliacea, Quoy. 



7. granulosa, Adams. 



8. imbricata, Gould. 



9. Mitrula, Sow. 

 10. orientalis, Dufo. 



11. Panamensis, C. 5. ^. 



12. radiata, Q«oy. 



13. subrufa, Mart. 



14. Ticaonica, Sow. 



15. trigona, Crme£. 



Genus 3. CALYPTRJEA, Lamarck. 



Animal ; with a broad and slightly produced muzzle ; tentacles 

 two, rather short, lanceolate, unconnected, with the eyes on 

 bulgings at their external bases ; mantle with a simple edge ; 

 branchial plume single; foot suborbicular, slightly angled in 

 front ; its sides plain, sometimes secreting a basal plate. 



Shell ; globosely conical, thin, irregular, generally beaked at the 

 top, transparent-white, radial ely densely very minutely striated, 

 with an internal, oblique, semifunnel-shaped apjjendage. 



The Cup-and-Saucer Limpets associated by Lamarck under this head 

 require to be separated into three genera. Calyptraa, in its restricted 

 sense, includes thirty-three species, all having a shell of peculiarly fine, 

 semitransparent, thread-like tissue, with a slender, erect internal appen- 

 dage, like the half-section of a funnel, and some of the species secrete a 

 well-formed basal plate. The larger Lamarckian Calyjdrcece, having an in- 

 ternal appendage in the form of a distinct cup, are included under genus 

 Crucibulum ; and those in which the internal appendage forms a trochoid 

 septum, under genus Trochita. 



The circumstances which led to the necessity of making this change are 



are hollow : the upper valves are also somewhat modified in form by the same cause, so as to be 

 more or less regular according as the lower valve has adhered to a more or less smooth and even 

 part of the stone. The attached valves have not attained a great degree of thickness, conse- 

 quently I do not suppose any one of the individuals to be of advanced age ; there are, however, 

 several which can only just have occupied their positions on the stone : these are not above 

 -£s part of an inch in diameter, and they show the perfect point of the upper valve, somewhat 

 convoluted aud inclined toward the anterior edge. Other individuals, which are placed in a 

 cavity of the stoue, are very regular in shape, but have their ridges slightly curved upwards 

 in conformity with the nearly regular vesicular shape of the cavity The edges of the lamella 

 near the outer margin in most of the specimens are furnished with a thin fringe of epidermis, 

 but the very young shells are destitute of this. An individual of Hipp, subrufa is observable 

 among the group of Hipp. Mitrula : its apex is distinctly spiral and its epidermis hairy. 



" The second specimen belongs to the species which I have named Hipp, barbata. This is 

 a very complete specimen, and reminds me of the beautiful fossil species Hipp. Cornucopia ; 

 it is a small individual, having its attached valve very much thickened and adhering to a much 

 larger one of the same species ; its edge is much elevated, and it is deeply concave ; the free 

 valve is rather smaller, and conical, and its edge is surrounded by the elevated edge of the 

 attached valve." — -Sowerby, Pro. Zool. Soc, 1835, p. 4. 



