72 



G. LINDSXIJOM, IlELIOLlTID.i;. 



Tribus II. PlasinoporiiirB. 



The inost prominent, distinguishing feature of tho genera cotnposing this tribus is 

 the constitution of their coenenchyma, almost entirely made up of thin, convex, minutc 

 lamellaä, which, superimposed upon each other, form a vesicular tissue. As may be induced 

 from the coenenchyma of a few Plasmoporte (Plasra. stella, Pl. scala, pl. v, f. 21, 28) where 

 the Heliolitic type of coenenchjana is coordinate with the vesiculous, the convex lamella3 

 are undoubtedly homologous with the regular horizontal tabulas in the coenenchyma of 

 the genus Heliolites or, as it were, the convex laraella; are convertible into horizontal 

 tabute and vice versa. Another characteristic of the Plasmoporinse consists in the ])resence 

 of unconnected rods, slender rods (bacilli) or thick rods {baculi)^ standing errect or vertical in 

 the midst of the vesicular tissue (pl. vii, f. 13, pl. x, f. 9, 18) as already has been mentioned 

 above at pages 11, 12. To these may also be numbered the frequent, vertical acute which 

 have grown on the convex lamelte, either dispersed without order amidst these or being 

 disposed in several coordinate or juxtaposite longitudinal rows (pl. vii, tig. 10), though 

 without any connection with each other, but, as it were, foreshadowing the long, vertical 

 bacilte, which united alongside which each other, at last formed coenenchymal tubuli. 



The septa have spiny margins or thiiir lamina3 are entirely dissolved into rows of spines, 

 wliich are directed in the same way as the elementary fibrilte, of which they in reality are 

 compounds. The calicinal tabute are generally horizontal or concave as in the genus Heliolites. 



The modes of reproduction are also identical. 



Before giving a description of the genera cornposing this tribe it may be convenient to 

 review the characters given by Milne Edwards and Haime to the three genera which they 

 considered as most nearly allied and which also by låter authors have been grouped together. 



The following table gives a survey of the characters upon Avhich the said authors 

 based their new genera. 



The characters which are stated to be peculiar to each genus are i)rinted in italics. 



Plasmopora. 



Propora. 



Lyellia. 



1849. 



Poly|jier librc, subliéraisphérique, 

 a plateau co[iniiun recouvert 

 d'uiie épitlieque plissée con- 

 ceiitriquemeDt. Cloisoiis ru- 

 dimentaires. Plancliers hori- 

 sontaux. Murailles minces. 

 Calices å bords non saillants. 

 Les polypiérites sont unies 

 par d'assez grandes lames 

 verticales radiées, entré les- 

 quelles s'étendent d'aiitres 

 lames horizontales. 



Comptes Rendus, toiiie xxix, p 



Differe du genre précédant par des 

 calices k bords saiUaiHs, des 

 cloisons plus développées et 

 qui se prolongent extérieure- 

 nient sous forme de petites 

 cötes. 



262. 



