GENERA OF CH.ETETIDyE AND MONTICULirORIDyE. 271 



The genus Monticulipora was founded by D'Orbigny in 

 1850 (Prodr. de Pal., t. i. p. 25, where the date of the genus is 

 given as 1847); the only definition being: "cellules serrees, 

 poriformes a la surface, d'un ensemble rameux ou encroutant 

 couvert de petites saillies coniques." The first species given 

 under this definition is the well-known M. mamimdata, 

 D'Orbigny, of the Lower Silurian of the United States, which 

 must, therefore, be accepted as the type of the group. It will 

 be quite obvious that the only character in the above definition 

 which has the very remotest generic value, is the existence of 

 conical elevations or " monticules " upon the surface, and even 

 the nature of these elevations is left wholly undefined. The 

 genus Nebulipoi'a, M'Coy (Ann. Nat. Hist., ser. 2, vol. vi. 

 p. 282, Oct. 1850) was founded in the same year as Monticuli- 

 p07^a, and includes forms unquestionably congeneric with the 

 latter, though I am unable from his figures and descriptions to 

 be sure as to the precise species upon which M'Coy founded 

 his genus. This point, indeed, could only be set at rest by an 

 examination of the original specimens in the Woodwardian 

 Museum, which I have unfortunately had no opportunity of 

 inspecting. It is, however, a matter which, I think, will still 

 admit of discussion, as to whether or not M 'Coy's Nebtilipoi'a 

 should not be adopted as the title for the fossils now under 

 consideration, rather than the Moiiticitlipora of D'Orbigny. I 

 am not able to decide this point, and I will only remark, further, 

 that M'Coy, in his generic diagnosis, states that the walls of 

 Nebulipora are " apparently perforated by rows of small fora- 

 mina," though he does not allude to this character again, and 

 seems to have been doubtful as to its actual existence. The 

 typical Montictiliporce seem to be undoubtedly devoid of mural 

 pores ; but I have examined (through the kindness of my 

 friend Mr R. Etheridge, jun.) a specimen from the Wenlock 

 Limestone of Dudley in the collection of the British Museum, 

 which has all the external and general characters of such 2^Mon- 

 ticidipora as M. petropolitana, Pand., but in which the walls of 

 the corallites are unquestionably minutely porous. It is not 



