Prof. M. Schultze on Polytrema miniaceum. 421 



lida, with a calcareous porcellanous shell ; and 3, Lituolida, with 

 a calcareo-siliceous shell containing sand-grains : of the Per- 

 forata — 4, Lagenida, with very fine pore canals ; 5, GloUgeri- 

 nida, with larger pore canals; and 6, Nummulinida, in which, 

 in addition to the ordinary pore canals, never usually very fine, 

 there is a system of peculiar cavities and canals, giving the shell 

 a very complicated structure. The families are sometimes very 

 large, and might well be divided into subfamilies, which would 

 nearly agree with the families established by me, — for example, 

 Carpenter^s Miliolida into the true Miliolida, the Peneroplida, 

 Soritime {Orbitulitince) , Alveolinidee, &c. From the wonderful 

 perseverance and great skill which Carpenter has shown in his 

 researches upon the shells of the Polythalamia during many 

 years, and considering the enormous amount of materials, con- 

 sisting of the most various forms from every zone, which he had 

 at his disposal, one can understand how he comes to undervalue 

 a little the works of his predecessors, and especially mine, in so 

 far as they treat of the shell-structure. Indeed it was the chief 

 object of my researches to ascertain the exact nature of the ani- 

 mal body which inhabits and forms the shell, for which reason 

 I confined myself especially to the forms observed by me in a 

 living state, and their nearest allies. Moreover, although I was 

 assisted by many of my friends, I found it impossible to bring- 

 together all the species, as I desired and indeed required for the 

 elaboration of a systematic revision. Por example, I was almost 

 entirely destitute of the living species of Carpenter^s Nummu- 

 linida, and thus had not the opportunity of seeing the system 

 of ramified tubes first described by Carter, as stated at page 15 

 of my book. Nevertheless my observations upon the shell- 

 structure are not so scanty as Carpenter seems to suppose. In 

 opposition to his repeated assertion*, that I have too much 

 neglected the investigation of the shell-structure, and confined 

 myself to the examination of the animal, I may be allowed to 

 urge that, independently of the representations of the shell- 

 structure of the species observed living by me, such as Polysto- 

 mella strigillata (pi. 4 & 5. figs. 2, 6, 7, 9, 10), P. gibba, P.steUa,P. 

 borealis, and P.venusta (pi. 6. figs. 2, 5, 8), of which I think I may 

 assert that they are not exceeded by Carpenter's, there are in va- 

 rious parts of my work (especially in the chapter " On the Shells 

 of the Marine Rhizopoda," and in section iii. p. 37) a great num- 

 ber of remarks, founded upon personal observation, as to the 

 structure of numerous exotic Rhizopod-shells, such as the Sori' 



* Phil. Trans. 1856, p. 187 ; Introduction to the Study of the Foramini- 

 fera, p. 10. 



