Section IV., 1885. [ 29 ] Trans. lioY. Soc. Canad.v. 



lY .— Illustrations of the Fauna of the St. John Group continued. No. III. — Descrip- 

 tions of new Oenera and Species, {including a description of a new Species of 

 Solenopleuni hy J. F. Whiteaves.) By Geo. F. Matthew, M.A. 



(Presented May 2G, 1885.) 



The. accumulation of material has made it necessary to change the plan ol' this memoir 

 to some extent. It was begun chielly with the object of exhibiting the va.riatio]is observa- 

 ble in the trilobites of the above-named formation ; but so many interesting forms belong- 

 ing to other groups of the animal kingdom have been met with in the material examined, 

 that the author thinks a description of these will be a useful preliminary to further study* 

 of the development and variation of Ibrm in the several species. 



I.— PROTOZOA. 



Several organisms of the grouf» Calcispongia occur in the strata of Division 1, and of 

 these the airthor here describes one which can easily be recognized by its external form. 



ARCHEOCYATHUS, Billings. 



Under this name Mr. Billings has described, from a limestone of Potsdam age in 

 Labrador, certain sponges which, in the appearance of their outer and inner walls, ajid the 

 intervening loculi, resemble the species the author is aboiit to describe ; but they differ from 

 it in general form, and are much larger. It is proposed, however, to describe the species 

 above referred to under this genus, pending a more extended and careful examination of 

 the more ancient fossils of this kind. 



Archeocyathus ? PAVONOIDES, u. sp. (Plate V. Figs, la, b, c and d) 



General form that of a more or less flattened disk, with ascending and irregularly 

 cylindrical branches ; these branches are generally hollow, though sometimes filled with 

 a cellular mass, traversed" l)y irregular loculi. Next the outer wall of the cylindrical 

 branches or tubes of the skeleton, the arrangement of the pores or openings is more 

 regular ; here may be recognized the inner surface of the wall, marked by transverse 

 parallel projecting lines of growth, which encircle the alternately expanding and con- 

 tracting, ascending branches; there are less distinct longitudinal lines or strire, which 

 connect and often traverse the surface of these engirdling ridges, giving the surface a 

 cancellated appearance : the outer surface of the wall is marked by close-set pits or pores, 

 and shows a faint longitudinal striation between the numerous pores with which the 

 surface is studded. The outer and inner walls are frequently seen to be separated by 



