BRYOZOA. 469 



DIAMESOPORA COMMUNIS Ulrich. 



PI. XXXIX, Fig. Sa, and PL XLI. Fig. 5-5b. 



This species is closely related to the preceding, but differs in 

 being more robust in growth, in having well marked maculae, 

 with subsolid centers, from which the cell apertures radiate out 

 in all directions. The apertures immediate surrounding the 

 maculae are also slightly larger than the others, while an ob- 

 scure concentric arrangement prevails. On the whole, the cell 

 apertures are also somewhat larger, and the peristomes thicker. 



Position and locality: Cincinnati group. 



This form is commonest in the layers exposed in the river 

 bank opposite Cincinnati, 0., where D. vaupeli is not known to 

 occur. It has a vertical range of about 125 feet, and in the 

 last 25 feet, the two species are found associated. 



CREPIPORA Ulrich, 1882. 



(Jour. Cin. Soc. Nat. Hist.. voL V, p. 157.) 

 (For generic diagnosis see page 380.) 



This genus differs from Ceramoporella Ulrich, mainly, in the 

 nearly complete restriction of the mesopores to the maculae. 

 These usually form a conspicuous feature of the surface. The 

 lunarium is also better developed and the zooecia apertures 

 much less oblique than is usual in that genus. (7. impressa and 

 C. solida. however, are closely related to some of the aberrant 

 forms now classified with Ceramoporella. 



Five representative species are here described, which, com- 

 bined, furnish a good idea of the limits of the genus. The sub- 

 ramose, hollow branched species, described by me as Chsetetes 

 venustus* although differing widely in its habit of growth, is 

 nevertheless closely allied to C. simulans. the type of the genus. 

 Beside these, my cabinet contains material of four or five un- 

 described species, all of them from the Cincinnati group. An 

 Upper Silurian species, closely related to C. epidermata, occurs 

 at Gotland. It is known to European palaeontologists as Dis- 

 copora squamata (Lonsdale sp.) 



