CRANIA 



Retzii et Aiictorum. 



TESTA inaeqiiivalvis, aequilatera (subirregularis) 

 orbiculari-subquadrata, eompressa : valvuld su- 

 perior e patelliformi, inferior e affixa planulata. 

 Impressiones muscular es in utraqiie valvule, 

 quatuor; quarum duae in inferiore subcen- 

 trales, approximatae, duae posticse, submargi- 

 nales, distantes. Cardo edentulus. Ligamen- 

 tum nullum. 



A Genus belonging to the family of Terebrahdoid shells, 

 the Brachiopoda of Cuvier, but placed by Linneans in Ano- 

 mi'a, where it is united with Placuiia, the true AnomicB and 

 other shells of very different characters ; and by Lamarck 

 among his Rudistes, evidently because he was unacquainted 

 with the animal inhabitant. Poll, who has named the 

 animal Criopiis, has, hoAvever, published the detail of its 

 anatomical structure, in which it entirely accords with 

 the rest of Lamarck's Brachiopoda ; and Ave have had an 

 opportunity of examining a dried specimen of the animal 

 which distinctly shows its two characteristic fringed arms 

 or tentacula. Lamarck has confounded his own Genus 

 Orhicula with it, and indeed almost every author who has 

 touched upon either genus has committed some error ; in 

 the 13th vol. of the Linn. Trans, we have endeavoured to 

 unravel the confusion that has been thus created, and to 

 assign to each genus its peculiar characters ; the following 

 are those by which Crania may be knoAvn : 



Shell inequivalve, generally equilateral, rather irre- 

 gular, orbicularly subquadrate and flattish; the upper 

 valve patelliform, having its umbo or vertex rather be- 

 hind the center; the lower valve attached by its outside, 

 the greater part of it being generally extended over the 

 siubstance to which it adheres; (and in this respect it dif- 



