188 SYNOPSIS OF THE CHARACTERS OF THE 



AsTRiEA PENTAGONA. Blain. 



Astrgea pentagona. Lonsd. Geol. Trans Astraea pentagona. Phil. Pal. Fos. 



This species differs from the last, principally in the fewer lamellaj, and the greater distance between 

 them ; and in the margin of the stars being bent or indented in a zigzag manner, by the extremities of the 

 lamellae on each side. 



LiTHOSTROTION. Park. 



Columnaria. Goldfuss. 



Gen. Ch. — Coral, composed of adhering, prismatic, parallel tubes; each having a single, terminal star. 



LiTHOSTROTION STRIATUM. Park. 



Lithostrotion striatum. Park. Organ. Rem Cyathophyllum basaltiforme. Phil. Geol. York. 



Sp. Ch. — Tubes prismatic, irregular, polygonal, longitudinally or transversely striated ; marginal lamellae, 

 about forty, commencing within a crenulated vertical dissepiment. 



This beautiful fossil occurs occasionally in abundance ; it varies considerably in the number and shape of 

 Its sides, these are usually plane, but sometimes specimens occur in which they are convex ; the striation 

 vanes from longitudinal to transverse, and the diameter of the tubes, from three to six lines ; but so irregu- 

 larly are those characters distributed, sometimes in the same specimen, that it is obvious they all belong to one 

 species. 



LiTHODENDRON. Schweig. 



Gen. Ch. — Coral, cylindi'ical, branched, adliering by the base, each tube with a single, terminal, stellular 

 disc. 



LiTHODENDRON AFFINE. Mart. SP. 

 E. Madreporites affinis. Martin, Pet. Derb. — Lithodendron longiconicmn. Phil. Geol. York. 



Sp. Ch. — Tubes thick, loosely branched, exteriorly smooth ; lamellse sixty-four, alternately longer and 

 shorter. 



This large species occurs usually in thick beds or masses, often of great size ; it is easily known from the 

 other species by its smooth surface. Diameter of the tubes about five lines. 



LiTHODENDRON CiESPITOSUM. Mart. SP. 

 E. Madreporites ca;spitosa. Mart. Pet. Derb. — Lithodendron fasciculatiun. Phil. Geol. York. 



Sp. Ch. — Tube fiexuous, irregular, slightly nodulous ; longitudinally striated ; lamellae about twenty-five 

 within, fifty without. 



This species forms bundles or masses, often of extraordinary extent, in certain localities ; the tubes are 

 irregularly wrinkled concentrically, and marked with obtuse, smooth, longitudinal striae. Diameter of tubes 

 four lines. 



LiTHODENDRON COARCTATUM. Portk. 



Lithodendron coarctatum. Portk. Geol. Eep. 



I have only seen one bad specimen of this species ; the tubes are smooth, crowded, little more than a 



line in diameter. I am not aware of the differences which are supposed to exist between this species and the 



L. sexdecimale of Phillips, Geol. York ; the specimen I have seen is not good enough to determine the 



question. 



