Dr. Alex. Broicn — On Solenopora. 151 



there, which are, in all probability, the remains of the reproductive 

 organs (conceptacles). In tangential section the cells appear more 

 or less rounded, and also often polygonal. Cell-division is active, 

 and where the cells are not polygonal intercellular spaces are observed 

 to be present. In certain sections are found spaces of a rounded or 

 oval character ; and, further, in the same specimens, are observed 

 at intervals clusters of cells arranged in a rosette-like fashion (see 

 Fig. 5). This latter condition may simply be due to the results 

 of cell-division ; but to this I shall refer later on. The empty 

 spaces maj' be all that is left of former reproductive organs. 



Fig. 5. — Tan^. sect, of Solenopora Jtcrassica, Nich. (MS.), from Malton, Yorkshire, 

 showing rosette-cells and spaces (coaceptacles). x nearly 50 d. 



In one specimen from Malton these spaces are arranged in a row, 

 but there was great difficulty experienced in getting good sections 

 for examination, on account of the imperfect state of preservation. 



Observations. — This is the only species of Jurassic age yet known. 

 It occurs under the same conditions as the other species. The 

 form of its cells has already been shown to be similar to those of 

 Solenopora nigra. The distinct nature of cell-walls, both transverse 

 and longitudinal, places it apart from all the other species. 



Formation and Locality. — Jurassic, Great Oolite, Chedworth, 

 Gloucestershire, and Malton, Yorkshire. (Coll, H. A. Nicholson.) 



EXPLANATION OF PLATE V. 



Fig. 1. — Vertical section of a Tertiary NuUipore {LitJiothamnion), from " Leitha- 



Kalk" of Austria, x 25 d. 

 ,, 2. — Vertical section of Solenopora lithothamnioides, n.sp., from Shalloch Mill, 



Girvan, Ayrshire. The specimen shows concentric layers of cells, each. 



layer being composed of numerous cells arranged in parallel rows. 



X 12 d. 

 ,, 3. — Vertical section of Solenopora nigra, n.sp., from the Ordovician Limestone 



of Saak, Esthonia. x 25 d. 

 ,, 4. — Vertical section of Soleyiopora fusifonnis, n.sp., from Craighead, Girvan. 



A great part of the specimen is destroyed, and the structure obliterated 



by secondary crystallization, x 12 d. 



(lb be continued in our next Number.) 



