BIROSTRITES 



Lam. Hist. Nat. des Aiiim. sans vert. VI. pt. 1. p. 235. 



TESTA inaequivalvis, bicornis; valvis disco ele- 

 vate conicis, inaequalibus, oblique divaricatis, 

 subrectis, corniformibus ; altera alteram basi 

 obvolvente. 



The Birostrites is^ indeed, a most singular fossil. Accord- 

 ing to Lamarck, it is composed of two pieces or valves 

 which do not unite at the edge of their bases, but of which 

 the longer and larger envelopes the other, and the dorsal 

 disk of each is elevated into the form of a nearly 

 straight cone, slightly arched interiorly. These horn- 

 shaped valves are unequal, and diverge obliquely in the 

 form of a V, whose branches form a very obtuse angle, 

 and unite at their bases. 



We have copied the character of the Genus from 

 Lamarck, and we have as above endeavoured to translate 

 as correctly as possible the greater part of his observa- 

 tions. He further says, that this Genus is assuredly very 

 different from his Diceras, and that the inside of the shell 

 is not known : having, however, formed our own opinion 

 from an examination of a cast of the inside, we venture to 

 differ from him, and to express our conviction that it 

 ought to be placed next to Diceras, or at least in the same 

 family with Chama and IHceras, (inasmuch as it accords 

 very nearly with those shells in its internal characters,) 

 and that it should not be placed in his family of Rudistes : 

 indeed, the whole family of Rudistes might be struck out, 

 and of the six genera which compose it, we believe 

 Sphcerulites and MadioUtes are not shells | Cakeola most 



