INTIMATE STRUCTURE OF THE SHELLS OF BRACHIOPODA. 35 



Family— RFIYNCONELLIDtE. 



In the shells of this family, I believe the absence of the perforations to be a character 

 as constant, as their presence is in the Terebratulida. No one who examines the shells of 

 the recent Hhynconella psittacea and Bh. nigricans, even in the most superficial manner, 

 can have any hesitation in recognizing the entire absence of the superficial "punctuations" 

 which mark the orifices of the shell-canals in the recent species of Terebrafididce ;^ and 

 the most careful microscopic examination of these sections of the shell, taken from any 

 part, and in any direction, does but confirm this conclusion. Thus, in Plate V, fig. 4, is 

 shown a considerable area of the interior of the shell [a, a), which displays the usual 

 imbricated arrangement of the extremities of its component prisms, shown on a larger 

 scale in fig. 5 ; whilst these prisms are exhibited in their longitudinal aspect by a fracture 

 of the shell at b, h. In neither part can the least trace of perforations be seen.^ In all 

 other respects, the intimate structure of the shell corresponds precisely with that of 

 Terebratulidce ; but it may be mentioned that the prismatic laminae are less adherent to 

 each other than in the perforated shells, so that they are readily split asunder, this being 

 the case with the fossil no less than with the recent species 



Rhynconella. — Recent, psittacea *,^ nigricans *; — Fossil, acuta, concinna, decorata, 

 depressa, inconstans, lata, nucella, obsoleta, octoplicata,* plicatella, j^ggniea, rostrata, spinosa, 

 subplicata, tetraedra. — The only peculiarity which I have met with among these, is a 

 peculiar oblique striation of the prisms of Bh. octopUcata, already described (p. 27). 



Camerophoria ScJdothemii, not perforated. 



Pentamerus Knightii, not perforated. 



PoRAMBONiTES. — It is uot a little remarkable that in this genus the shell should be 

 most unequivocally non-perforated, notwithstanding that the punctuation of the surface, in 

 one species especially, has led to the supposition that large " pores" exist, whence, I 

 presume, the generic name has been derived. The most careful microscopic examination 

 of transparent sections, fails to bring into view any perforations either in P. aqmrostris or in 

 P. reticulata. 



' In Mr. G. B. Sowerby's 'Monograph of the Genus Terehratula' in which these two species are 

 described under that generic designation, they are spoken of as " the only species that are not 

 punctuated." 



2 I cannot refrain from here again expressing my astonishment, that any systematist should venture to 

 affirm the universal existence of perforations in the shells of Brachiopoda, without having examined one of 

 the most common of the recent types of the group, in which the absence of such perforations had been 

 specified as a distinctive character by competent observers. 



3 PI. V, figs. 4, 5. * PI. V, fig. 6. 



