164 REPORT— 1881. 



pai't, is the Microporella of Hincks, a geuus wliicli includes species 

 selected from no fewer than ten genera of recent and fossil Polyzoa. 



Laying aside the genus Ptilodictya, I have no knowledge of any other 

 Palseozoic Polyzoa that can be, even provisionally, placed with the Cheilo- 

 stomata. After careful consideration I am reluctantly obliged to say that 

 at present there is no evidence that the sub-order existed in any of the 

 Palaeozoic seas, and further, the evidence is very doubtful until we reach 

 the Mesozoic era. Notwithstanding this decision I shall be amongst the 

 first to acknowledge the ea,rlier existence of types if well-defined evidence 

 is brought to bear in the diagnosis of new discoveries. 



Taking into consideration the shape and character of the cell as pre- 

 senting, apparently, an Eschuridie type, I think I cannot do better than 

 begin this Report with a revision of the whole of the PtUodicfya. M'Coy ' 

 places this genus as the fourth in his Family Escliaridm ; Berenicea being 

 the third genus in the family. From the characters given, ' cells shal- 

 low, oblong, or ovate, often provided with an operculum, capable of being 

 closed by special musdeti,' M'Coy evidently believed that the Palteo- 

 zoic species could be naturally placed in this Family. The true EsCHA- 

 RiD^ are of later date, probably not older than the Lower Oolite, and 

 then not as a typical, but only as a kind of passage group. Leaving the 

 classification as an open question at present, I shall take Lonsdale's defi- 

 nition for the group as redescribed by M'Coy : — 



1839. Ptilodictya, Lonsdale. 

 1847. Stictopora, Hall. 



' Zoarium- thin, calcareous, foliaceous, or bi-anching dichotomously ; branches 

 sometimes coalescing : a thin, laminar, flattened, concentrically wrinkled 

 central axis ; set Avith oblique, short, subtubnlar, or ovate cells on both 

 sides, with prominent oval mouths, nearly as large as the Cells within ; 

 branches often flattened, with the margin solid, sharp-edged, striated, and 

 without cells ; the boundary ridges of the cells square or rhomboidal.' 



This genus is very fairly represented by specimens in the School of 

 Mines. There are no fewer than ten species named, and three marked 

 ' New Sp.' awaiting description. Accepting the w-ork of other authors, 

 I can do no more than furnish notes on them, just as they are named. 

 The first specimen is P. dichotoma, Portlock, in the Wyatt-Edgell Col., 

 and is found in the Lower Llandeilo flags, and the species ranges into 

 the Upper Llandeilo and Caradoc. In the Caradoc, also, we have the 

 P. acuta, Hal], which, if correctly identified, is very widely distributed in 

 the American and English Silurians of the same horizon ; and P. explanafa, 

 M'Coy. Three species undescribed, but bearing MS. names by Mr. 

 Etheridge : P. papilMa, P. ramosa, F. scutata. In the Lower Llandovery 

 we have the P. fucoides, M'Coy, a species having a very limited range. 

 .In the Upper Llandovery we have P. lanceolata, Lonsd., which ranges 

 through the Wenlock Shale, Wenlock Limestone, Lower Ludlow and 

 Aymestry Limestone. There is a departure from the type in P. scalpellum 

 (Eschara? scalpedhim, Lonsd.); it is marked as appearing in the Upper 

 Llandovery and "Wenlock Limestone. Hall, in the first vol. of the 'Pal.,' 

 New York, figures and describes P. (Stictopora) acuta, which he compares 

 with this species of Lonsdale. In this species, too, there seems to be no 

 central laminar axis. It is found in the Trenton Limestone. With regard 



^ ^rit. Pakeozoic Fos. '■ CoraTbmx, Lonsdale, M'Coy's Pal. Fos. 



