198 ORGANIC REMAINS. 



Most of these branched corallites, found in our oolite, are highly 

 crjstalline or sparry; so that their cross fractures shew little of then- 

 internal organization. In the fungiform kind and others above- 

 mentioned, there is generally very little spar; the septa or lamellae 

 being often highly siliceous, and the interstices filled with a less 

 compact matter, chiefly calcareous. Such fossils are frequently 

 dipped in acid, to dissolve the calcareous matter adhering to them 

 when recently found, and display the edges of the lamellaB more 

 fully. When they have passed through this process, their surfaces 

 appear finely glazed. 



But the most beautiful of our fossil corals are those which pre- 

 sent an assemblage of stars on their upper surface; and especially 

 those in which the stars are connected into a system, and disposed at 

 regular distances. Of these, one of the most common, and at the same 

 time the most beautiful, is that of which a specimen is given in Plate 

 IV, No. 2. It corresponds with the recent madrepora ananas; having 

 the stars arranged in hexagonal or pentagonal compartments. Each 

 star is deeply depressed on the disk, and has usually a minute cone, 

 or papilla, rising in the centre, and is inclosed by an elevated circular 

 margin, on the outside of which are fine diverging stria, filling up the 

 rest of the hexagonal compartment. These minute stripes are not 

 represented in the figure; in which also, the hexagonal septa are 

 made much more distinct than they are in the fossil. The specimen 

 is from the oolite at Helmsley, and consists chiefly of chert, or rather 

 of calcedony. Madreporites of the same kind occur at Malton and 

 other places. Polished sections of them exhibit a beautiful net-work, 

 which is well represented in Parkinson's Org. Rem. II, PI. V, Fig. 1 . 

 Another beautiful madreporite of this family also occurs in the 

 Malton oolite, bearing a considerable resemblance to the last, but 

 having neither the elevated circle, nor the central papilla ; the stri(B 

 formed by the edges of the lamella, proceeding from the centre, which 



