Bryo%oa, 



61 



therefore, though the exhibition series of British species is fairly 

 complete, only a few representatives of the foreign forms are 

 exhibited. The main series of British Bryozoa are exhibited in 

 two high tables in the centre of the gallery. Specimens too large 

 for this series, and the foreign forms, are in Wall-case 12a. 



Commencing with the central table-cases, we find in the first 

 place a series of specimens from the Ordovician rocks of Wales. 

 These are in an unsatisfactory condition of preservation, and they 

 can only be determined by the assistance of better specimens 

 yielded by rocks of the same age in America. One species is 

 referred to the existing genus Berenicea, but the rest belong to 

 two extinct orders — the Trepostomata and Cryptostomata. 



In the Silurian deposits the Bryozoa are in more perfect con- 

 dition, and the specimens from the Wenlock Limestone include 

 some interesting and elegant forms, such as Ptilodictya suhlanceo- 

 lata, Penniretepora Lonsdalei, and several species of Fenestella and 

 Polypora. 



Bryozoa. 



GALLERY 

 VIII. 



Centre - 



86a & 86b, 

 Wall -case 

 12a. 



Fig. 104. — Botryllopora sociale, Nicli. 

 Devonian : Canada. a, portion of 

 HeUophyllum with a small group 

 of discs of Botryllopora adherent 

 to it (nat. size), b, a single disc en- 

 larged ; 0, one of the radiating ridges 

 enlarged to show the cells. 



Fig. 105. — Streblotrypa Hamil- 

 ^o«(?«sis, Nich.,sp. Devonian: 

 Canada. a, nat. size, and b, 

 enlarged, to show the cells 

 and the tubular intercellular 

 interspaces. 



The Devonian fauna is small, and the specimens are not well 

 preserved ; the type-specimen of Fenestella prisca (Phil.) is the 

 best in the series. The Carboniferous Bryozoa, on the other hand, 

 are numerous and in good condition. The most important genus 

 is Fenestella-, the size to which colonies of this attain is shown 

 by two specimens mounted on blocks in Wall-case 12a. The Wall-case 

 fan-shaped species of this genus and of Ptilopora, the feather- ^ * 

 shaped Penniretepora, and the cylindrical Rhomhopora, are the 

 most interesting forms in the table-case. Hemitrypa should not 

 be overlooked, as it consists of a colony formed of two layers, of 



