CRENATULA. 



eular impression is very indistinct, it is, however, of an 

 oblong form and placed near the anterior edge of the 

 pearly part of the shell. By far the greater part of the 

 shell of the Crenatulce is of the same leafy substance, com- 

 posed of perpendicular fibres, as the outside of Ostrea^ 

 Perna^ Malleus^ &c. We cannot tell whether or not Cre- 

 natula has a byssus, we understand it is found imbedded in 

 sponges. Lamarck describes several recent species in his 

 " Animaux sans vertehres^^^ which are all marine ; he says, 

 they are rare, as yet but little known, and that they are 

 brought from the seas of warm climates : two of our speci- 

 mens are from the South Seas. We do not know of any 

 fossil species; for both the fossils which Parkinson has 

 figured as probably belonging to Crenatuhy possess the 

 characteristic mark of Perna. 



On account of the near resemblance of Crenatula to 

 Inoceramus^ we may be expected here to explain the dif- 

 ferences between the two genera, but as the original ac- 

 count of Inoceramus will shortly appear in the Trans, of 

 Linn. Soc. we must decline it for the present, intending to 

 take the earliest opportunity of presenting our readers 

 with as complete an account as possible of that Genus. 



Fig. 1, 3. Crenatula avicularis' 

 2. mytiloides. 



