138 Dr. W. B. Carpenter on Spirifer cuspidatus. 



Figs. 14, lo, 16. Cells from the surface of the latter. 



Fig. 17. Cells from the stratum containing the pigment of the true eye. 



Fig. 18. The true eye of Margarita grd?ilundica, from the side. 



Fig. 19. The same, from the front. 



Figs. 20, 21, 22. Ismaila monstrosa, in different positions. 



XIII. — On Spirifer cuspidatus. 

 To the Editors of the Annals and Magazine of Natural History. 



University of London. 



Gentlemen, July 20, 1868. 



I have no intention of discussing with Prof. King the vali- 

 dity of the generic distinction which has been affirmed to 

 exist between Byringothyris and Spirifer .^ since this distinction 

 was not laid down by myself, and the main question involved 

 in it lies beyond the scope of my own researches. But, for the 

 sake of those who are associated with me in this matter, I 

 feel it necessary to make a few remarks upon that portion of 

 his argument which relates to the microscopic structure of the 

 shell in these two types respectively. 



Prof. King, having been allowed, by the kindness of Mr. 

 Davidson, the fullest opportunity of examining the singularly 

 well-preserved specimen of Spirifer cuspidatus^ of which I de- 

 scribed the structure in my last communication on this subject, 

 and having found himself equally unable with myself to dis- 

 cern in it any trace of those perforations which he has so 

 persistently asserted to exist in that type, supplies the de- 

 ficiency out of the depths of his own inner consciousness. 

 ^' Impressed," he tells us, "with the preceding evidences and 

 considerations, I can only conclude that, wherever imperforate 

 spaces occur in Spirifer cuspidatus^ perforations were origi- 

 nally present in them. And although Mr. Davidson's speci- 

 men (also, it must be remembered. Prof. Harkness's) may be 

 noted as ^ exhibiting not the smallest trace of perforations,' I 

 have no hesitation whatever in adopting the same simple 

 conclusion in this case as well, rather than seek for its explana- 

 tion in any strange morphological doctrine." 



What '' strange morphological doctrine " is involved in the 

 assertion that the true Spirifer cuspidatus belongs to that " im- 

 perforate " type which 1 showed to exist among Brachiopods, at 

 the very time when I first demonstrated* that the " puncta- 

 tions" by which the true Terebratulidse and certain Spiriferidfc 

 are characterized are the orifices of '' perforations," I must own 



* Reports of the British Association for 1844. 



