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, millepora violacea 

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

 it-s polypiferous pores, he thinks requires to be separated 

 from that genus. 



1. Dist. 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, alcicornis, aspera, 

 truncata, tubuUfera, 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 agaridformis. 



None of these are represented as having been seen in a 

 fossil state ; but the separations adopted here and in the 



