FOSSILS AND ROCK-SPECIMENS. 593 



" several casts of a racemose Stenopora were noticed in the collection 

 [Count Strzelecki's] examined, but that they did not admit of com- 

 plete identification." It is highly probable that Mr. Forrest's speci- 

 mens belong to the species to which allusion is thus made. 



Genus Evactinopora, Meek and Worthen, 1865 *. 



This genus was instituted for the reception of certain peculiar 

 forms, which are, perhaps, more nearly polyzoan than actinozoan, 

 but which are not very easy to understand. The following is the 

 generic diagnosis : — 



" Polyzoum free ? consisting of a few large, more or less thickened 

 and solid calcareous plates or laminae, radiating from an imaginary 

 vertical axis, so as to present, in transverse section, a star-shaped or 

 cruciform outline. Bays thickest and most dense on the under and 

 outer edges ; thinner and penetrated on either side by the pores 

 within ; each apparently divided along the middle by a thin lamina 

 separating the inner ends of the pores of the opposite sides ; substance 

 showing in transverse sections a more or less laminated structure, the 

 laminae being arranged parallel to the planes of the rays. Pores 

 small, regularly arranged in quincunx, and separated by spaces 

 equalling or exceeding their breadth." 



Three species are described and figured from the Lower Carbo- 

 niferous of Illinois and Iowa. The authors allude to the possibility 

 of Evactinopora being the same as Conodictyum of Mlinsterf. 



4. Evactinopora crucialis, sp. n. Plate XXIII. figs. 2 a, 2 b, 2 c. 



Somewhat similar to Meek and Worthen's Evactinopora grandis 

 (op. cit. p. 503, pi. 15. fig. 2, 2 a, 2 b), this one differs principally in 

 the arrangement of the pores on the flanks of the rays. As may be 

 seen in the enlargement of one of the rays (fig. 2 c), the pores or 

 tubulated terminations leave quite a blank space or callus. This 

 peculiarity completely disturbs the symmetry of the qnincuncial 

 arrangement, whilst the pores themselves, as a sort of compensation 

 for being thrust out, are larger in immediate contiguity with these 

 blank spaces. 



The rays are four in number, as in Evactinopora grandis, and 

 arranged in the form of a cross ; the entire polyzoarium is very much 

 smaller, but this may be merely a question of age. The laminated 

 structure, mentioned in the diagnosis of the genus as being parallel 

 to the rays, is remarkably well shown by the artist both in the cross 

 section presented by the presumed base of the compound organism 

 (fig. 2 a), and still better in the fracture-face of the fourth ray, en- 

 larged (fig. 2 c). It is very evident that weathering developes and 

 perhaps exaggerates this structure. 



The specimen figured is the only one in the Forrest collection that 

 can, with any certainty, be referred to this species. 



* Proc. Acad. Nat. Sci. Philad. 1865, p. 165. Meek & Worthen, Geol. Sur- 

 vey, Illinois, vol. iii. p. 501. 



t G-olclf. i. 103, pi. xxxvii. fig. 1 ; cf. also D'Archiac, Mem. Soc. Geol. France, 

 vol. v. p. 369, pi. 25. fig. 1 (Conipora cladiformis). 



