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Cincinnati Society of Natural History. 



identity of Callopora and Fistulipora. At any rate it is very evident 

 that he did not pay as much attention to the type species of the for- 

 mer, as he did to the type species of McCoy's genus. The internal 

 structure of Callopora elegantula, Hall, as I have worked it out from 

 examples of the species presented to me b} T Prof. James Hall himself, 

 shows, first, that Nicholson's Callopora incrassata is as far removed in 

 its structure from the t}'pe species of Callopora, as McCoy's Fistuli- 

 pora minor; and second, that a large proportion of the heterogeneous 

 assemblage of forms placed by Nicholson in his division Heterotrypa, 

 have precisely the same general structure as C. elegantula. The 

 species in question are 31. (H.) ramosa, D'Orb., and var. rugosa, Ed- 

 <fc H., M. (H.) dalei, Ed. & H., 31. (II.) sigillaroidea, Nich., 31. (H.) 

 nodulosa, Nich., and 31. (H.) andrewsi, Nicholson. All these species 

 have a zoarium constructed in a precisely similar manner. In all we 

 have numerous interstitial tubes, which may be either rounded or sub- 

 angular, and always have more closely set diaphragms than the proper 

 or larger cells; the latter again in all have subcircular or ovate visceral 

 cavities (in tangential sections), surrounding which is a more or less 

 distinct ring of dark sclerenclvyma. All the tubes, however, are firmly 

 united together, and never, so far as I have been able to ascertain, 

 show any distinct boundary line between them. A fourth character 

 common to all, is found in the fact that the tubes in the axial region of 

 the zoarium may be properly divided into two quite distinct sets of 

 tubes, large and small, the latter (as is shown in transverse sections) 

 being nearly always more angular than the former. In a longitudinal 

 section the tubes immediately above their origin in the axial or 

 "immature" region, are crossed by more close set diaphragms than 

 when they have attained their full growth. This feature gives the 

 tubes, in their primitive stage, the appearance of interstitial tubes, 

 though 1 am far from asserting that any of the tubes in the axial 

 region, even in the earlier periods of their development, performed the 

 unknown functions of interstitial cells. At an}* rate, the character 

 under consideration is one of the distinctive features of Callopora, 

 and ma}* be more or less readily recognized in all the species of the 

 genus known to me. Besides the five species and one variety above 

 mentioned (C. ramosa, D'Orb., and var. rugosa, Ed. & H., C. dalei, 

 Ed. & H., C. nodulosa, Nich., C. sigillaroidea, Nich., and C. andrewsi, 

 Nich.,) the Cincinnati group furnishes at least four other species which 

 have the characters of Callopora, but are as vet undescribed. Of the 

 numerous species referred to the genus by Hall, I can at the present 



