on the Genera Orbktthi and Crania of Lamarck. 47 1 



1. CRANIA PERSON A 1 A. 



C. valvula superior tenuis lievis. Tab. XXVI. f. ;}. 

 Syx. Anomia craniolaris. Linn., <$-c\ 



turbinata. Poli, ii. p. 189. t. 30. 



Patella Kermes. Humphrey. 



distorta. Mont. Linn. Trans, xi. p. 19-5. t. 13. f 5. 



Crania personata. Lamarck, Anim. sans Vert. 138. 

 Habitat in mari Mediterraneo, coralliis adfixa ; et in mari Sco- 



tico, saxis adha3rens. 



Humphrey, who described the upper valve under the name of 

 Patella Kermes many years ago, afterwards discovered his error; 

 Montagu never had an opportunity of examining the shell in its 

 natural situation, or he would have undoubtedly discovered his. 

 The only difference observable between the specimens from 

 Shetland and those from the Mediterranean, is in the thickness 

 and irregularity of the lower valve ; those from the latter sea 

 being very thick and irregular ; whereas, those from Shetland are 

 much thinner, and more regular in their shape ; but this diffe- 

 rence I imagine may be easily accounted for from the different 

 situation of the respective specimens ; the one being found upon 

 rugged old corals, and the other being attached to a compara- 

 tively smooth stone*. 



2. CRANIA ANTIQUA. 



C. valvula superior radiatim striata, striis elevatis, ex vertice ad 

 marginem decurrentibus ; valvula inferior postice. produc- 

 ts Tab. XXVI. /. 4. 



* Since this paper was read, I have seen Poll's figure of this shell, which he calls 

 Anomia turbinata ; he also gives several views of the animal inhabitant, under the name 

 of Criopus, which is certainly strongly corroborative of my expressed opinion, founded 

 upon the observation mentioned above, that it belongs to the family of Terebratulidea. 

 I am concerned, however, to be under the necessity of stating, that Poli has confounded 

 Miiller's Patella anomala (the Orbicula of Lam.) with it, expressing his astonishment 

 at Miiller's not having observed the lower valve, and naming it Patella. 



3 p 2 This 



