Shell-structure in the Genus Lingula. 31 



oulate, whilst in L. anatina they are fibrillate and otherwise 

 structureless. 



3. In the recent species of Lingula, as far as seen, the tubules 

 are finer in the living than in the Palaeozoic species, as previously 

 pointed out by Hall and Clarke. 



4. It is obvious from the foregoing observations on L. albida, 

 that Dr. Carpenter had examined either that or an allied species, 

 when remarking on the predominant horny structure in the genus, 

 and on the canaliculate character of the horny layers. 



