Proceedings of the British Association, 443 



proving that the formation of this layer was not accomplished at once, 

 but was continued for some time ; and adduced other facts in support 

 of his view. Dr. C. then described the cancellated structure of the Ru- 

 distes ; to which there is nothing very analogous among recent shells ; 

 this structure is composed of a series of cavities, lying between the ex- 

 ternal and internal layers of the shell, and separated by shelly parti- 

 tions disposed with considerable regularity. These cavities may have 

 been filled, in the living shell, with animal matter. The Pleurorhyncus 

 hibernkus was stated by Dr. C. to possess this structure in common with 

 the Rudistes ; which is a confirmation of the views of those who, on other 

 grounds, had referred them to that group. Dr. C. then stated, in regard 

 to the Terebratulae, that the examination of a considerable number of 

 species had confirmed his previous statement, that the non-plicated, and 

 slightly-plicated species are characterized by the possession of the perfora- 

 tions in the shell first described by him ; whilst these are absent int he 

 deeply-plicated species. They exist in all the known recent species, ex- 

 cept Terebratula psittacea ; which has, on other grounds, been separated 

 from the rest, and has been referred to the genus Atrypa, several spe- 

 cies of which, examined by Dr. C, are also characterized by the ab- 

 sence of perforations. Dr. C. further alluded to several cases, in which 

 this mode of examination had furnished characters of great importance 

 in classification, and in the recognition of fossil shells; and he con- 

 cluded by drawing attention to certain structures contained in the shell 

 of the crab, and in the skeletons of the Echinodermata. With the con- 

 tinued assistance of the Association, he hoped to be able to present, 

 next year, a detailed report on these classes. His present report em- 

 braces the structure of the shells of the Brachiopoda ; and of the families 

 Placunidae, Ostracese, Pectinidae, Margaritacese, and Unionidse, among 

 the Lamellibranchiate bivalves. In conclusion, he requested the aid of 

 his auditors towards the prosecution of his researches, by the transmission 

 of fragments of recent and fossil shells (named) for examination ; and 

 he mentioned that the smallest fragment might be of essential service 

 to him. 



Prof. Phillips observed that this paper was an example of the man- 

 ner in which doubt was gradually removed, and certainty obtained in 

 geological inquiries. One object of these investigations was to ascertain 

 the true affinities of recent and fossil grades of animal life, and, by this 

 means, a knowledge was also obtained of the corresponding problem of 

 the condition under which animals and plants formerly lived. In these 

 researches the aid of the zoologist was most important ; and Mr. Phillips 

 contended, that calling in the aid of the naturalist and the chemist was 



