73 



5. 0. macropora. Rather flat, with the centre depressed ; rather 



large pores on each side. 

 Fossil. 

 .6. pileolus. Convex on one side and concave on the other; 



a groove round the margin, no pores visible. 

 Fossil. 



Distichopora. A stony, solid, fixed, ramose and rather 

 compressed polypifer. The pores stelliform, unequal and 

 marginal, placed on the two opposite edges, in longitudinal 

 rows, and in the form of sutures ; wart-like projections are 

 scattered on the surface of the branches. 



This genus is formed by Lamarck for the reception of 

 what has been considered as a millepore, millepcra viclacca 

 of Pallas ; but which from its form, and the arrangement of 

 its polypiferous pores, he thinks requires to be separated 

 from that genus. 



1. Dlst, violacea. Ramose, with flexuous ascending branches 

 smoothly compressed. Pallas. Zooph. p. 258; Ellis and Sol. 

 p. 140. 

 Not known fossil. 



Millepora. A stony, internally, solid, polymorphous, 

 ramose or frondescent polypifer, pierced by simple, not la- 

 mellated pores. 



The pores cylindrical, and perpendicular to the axis or 

 to the expansions of the polypifer ; for the most part small, 

 and sometimes not apparent. 



1 . With the polypiferous pores apparent. 



In this class are disposed the following species of Linnaeus, 

 Solander, &c. M. squarrosa, complanata, alcicomis, aspera, 

 truncata, tubulifera, pinnata, and rubra. 



2. With the pores scarcely or not at all apparent. (Nullipores.) 



Among these are placed, M. informis, racemus, fasciculata, bys- 

 soides, calcarea, and ayariciformis. 



None of these are represented as having been seen in a 

 fossil state ; but the separations adopted here and in the 



L. 



