NOHTHtTMBEltLAND ANB DURHAM. 91 



whose fullest development appears in Amoeba villosa ; and the 

 more numerous series which are possessed of a test or carapace, 

 whether chitinous or composite, are developments of a very 

 limited number of specific forms, their mere external features 

 whether of shape, size, or the material of which the test is com- 

 posed, varying with the nature of the influences to which they 

 have been subjected during growth, and yielding no characters 

 for generic or even specific divisions. 



These facts but little affect the importance with which minute 

 characters in the Foraminifera are to be regarded ; for the indi- 

 cations of climatal and bathymetrical conditions, which may be 

 obtained by their study, are of much value both to zoological 

 and geological science. No advantage would be gained by at- 

 tempting to alter the nomenclature so as to express the compli- 

 cated relationship just pointed out, even were this possible ; and 

 the Linnean binomial system possesses such obvious advantages 

 on the ground of convenience and simplicity, that it becomes 

 necessary to adhere to it even though the terms genus and species 

 be used in a purely conventional sense. 



The names used throughout the Catalogue are adopted, with a 

 little correction, from the Appendix supplied by Messrs. Parker 

 and Jones to Dr. Carpenter's " Introduction to the Study of the 

 Foraminifera" (page 809) ; but references are given to the figures 

 of the species in Professor "Williamson's "Becent Foraminifera 

 of Great Britain." Those who take interest in the subject I 

 would refer to the paper before mentioned ' ' On the Phizopodal 

 Fauna of the Shetlands,' 1 * in which some of the questions here 

 spoken of are treated at greater length, and a classified table of 

 nearly the whole of the British forms is given. 



The following are the types under which the forms enumerated 

 in the Catalogue may be grouped : — 



Cornuspira fotiaeea, Phil. 



Miliola Seminulum, Linn., including Biloculina, Trilocidina, 

 QuinquelocuUna, and Spiroloculina. 



Trochammina squamata, P. 8f J. 



Lituola nautiloidea, Lamh. 



* Transactions of the Linnean Society. Vol. XXIV, part III. 



