American Palaeozoic Bryozoa. 14.3 



between them, the intervening spaces being filled by structureless 

 sclerenchyma. Besides the connecting foramina, which are well 

 shown in a section of this kind, Dr. Nicholson has described "numer- 

 ous delicate radiating spines, which spring from the wall and are 

 directed inwards for a longer or shorter distance, usually falling short 

 of the center." 



In Heteropora conifera, Lainx., we have in the main the same in- 

 ternal characters as above ascribed to H. neozelanica, with this 

 difference, that in tangential sections, the spaces on the walls of the 

 tubes between the connecting foramina, are concentrically laminated, 

 and inclose a dark spot (or sometimes a light one), thus giving the 

 same appearance as is presented in species with numerous spiniform 

 tubuli. I have not been able to detect any traces of radiating " spines." 



In Heteropora pustulosa, Michelin, according to Jules Haime's 

 figures (Mem. de la Soc. Geol. de France, 2d ser., vol. v., pi. xi.), the 

 surface is covered with " monticules," and diaphragms are developed 

 in considerable numbers in the cortical portion of the zoarium. 



I have also examined three species of Heteropora, and one of 

 Zonopora, D'Orb., from the Cretaceous of Arkansas. One of the 

 species of Heteropora is very similar to H. conifera, Lamx. Another 

 is a small slender species reminding one in its external appearance 

 very strongly of Batostomella gracilis, James. The third is still more 

 slender. Zonopora, so far as I have been able to ascertain, differs 

 from Heteropora, only in having the interstitial cells aggregated into 

 groups, which may be drawn out laterally to such an extent that they 

 completely encircle the branch. The species from Arkansas is nearly 

 allied to Zonopora variabilis, D'Orb., from the Cretaceous of France. 

 The second species above mentioned, I will provisionally call Hetero- 

 pora consimilis, n. sp., and it ma} r be characterized as follows: 



Heteropora consimilis, n. sp. (Plate VI., fig. 11.) 



Zoarium growing in frequently bifurcating, rarely anastomosing, 

 small ramulets, with a diameter of about .1 inch. Branches expanded 

 at the base, and attached to some foreign substance. Surface smooth. 

 Cells, small, frequently contiguous. Cell-mouths, circular, about -p^ 

 inch in diameter, usually with thickened margins. Intertubular spaces 

 of variable width, occupied by irregular cells, the diamecer of which is 

 always less than that of the true zooecia. Interstitial cells never 

 developed in greater number than would constitute a single series 

 around the true tubes; the number of the latter in the space of .1 inch, 



