220 



HARDWICKE'S SCIENCE-GOSSIP. 



It is sometimes desirable to mount the parasitic or 

 filamentous forms in fluid, in order to see the vari- 

 ous attachments of the frustules. For this purpose 

 an asphalt or thin glass cell must be used. I have 

 used camphor-water as the medium, and it appears to 

 answer the purpose. After the object 1t'=- '"-^'' 

 arranged, and \\^^ r.u cn.a, me cover must be placed 

 in position ; this requires some little practice to do 

 successfully. A thin ring of gold size must be made 

 on the cell, upon which the cover must be placed 

 (care being taken to exclude the air) and pressed 

 down upon the ring of gold size. Wipe off the 

 superfluous water, and spin a ring of shell-lac or 

 sealing-wax varnish round the edge. When this is 

 hard, a ring of varnish should be put over it. The 

 best for this purpose is that described in a former 

 number, viz. that made of litharge and red and white 

 lead ; or a mixture of flake-white and damar varnish 

 (as used for mounting) will answer the purpose. The 

 white, sold in tubes, is best, as no grinding is re- 

 quired. In all fluid mounts, care must be taken to 

 fill up the angle formed by the slide and cover. This 

 is better done by successive applications than all at 

 once. In conclusion, I beg to observe that I do not 

 give these instructions as the best. Their chief merit 

 is that they are the results of experience, and that 

 with practice the manipulator will be able to produce 

 well-mounted specimens. 



CHAPTERS ON 



CARBONIFEROUS POLYZOA. 



No. III. 



By G. R. Vine. 



THE genus Polypora, M'^Coy, is another of the 

 fenestrate forms of Polyzoa which seems to 

 have been confined entirely, so far as we are yet 

 acquainted with the genus, to the Palceozoic rocks. 

 It had, however, a wide geographical range, and. 

 though not so varied in specific character as the 

 Fcneslclla, the individuals of certain species may 

 have been equally numerous. The " corallum " or 

 Polyzoary of the Polypora was either a delicate, or a 

 robust, reticulated calcareous expansion. The inter- 

 stices were round, bearing from three to five rows of 

 cell-openings, the margins of which are usually not 

 projecting. The interstices were connected by thin, 

 transverse, non-poriferous, dissepiments.* 



It is doubtful whether the genus had its origin 

 further back than the Devonian era. One doubtful 

 form, P. crassa (?), is named by Lonsdale as belonging 

 to the Upper Silurian, Dudley. From the Devonian 

 rocks of America, Prof. Nicholson has figured 

 and described two new species, P. piilchclla and 

 P. tenella, from Ontario, t and Prout has described 



• M 'Coy's " Carb. Fossils." 



t Geological Mag., 1874, and " Ontario." 



two others, P. Halliana and P. ttiberculata* From 

 the carboniferous limestone of Derby and Kildare, 

 M'^Coy figures and describes two species, P. dcndroidea 

 and P. verrucosa ; and P. marginata as rv'>»"'inig at 

 Killymeal. in Ti-pl^n^, tugetner with P. papillata. 

 Morris refers two species described by Phillips to 

 this genus, — Retepora laxa and R, polyporata (?), and 

 also the species Gorgonia faslitosa of De Koninck.f 



Fig. 167. Polyjiorafasiuosa* 

 De Koninck (India). 



Fig. 168. P. ttiberculata, 

 Prout, Hairmyres, Scotland. 



The last of these species had a very wide geographical 

 range, as it has been found in Ireland, Belgium, and 

 in India. "I have not been able to perceive," says 

 De Koninck, "any diff"erence between the Indian 

 specimen and those I discovered in the carboniferous 

 limestone of the environs of Ecoussinnes."J 



The species of Polypora most frequent in the shales 

 of Scotland is the P. tuberctdata of Prout. In the 

 explanation of sheet 23 of the Geological Survey of 

 Scotland, this species is referred to the P. verrucosa 

 of M'^Coy. "There are important characters to 

 show that it differs from M'=Coy's species. i. Its 

 manner of branching is different. M'^Coy says 

 that P. verrucosa rarely bifurcates in its interstices, 

 and that its fenestrules are equal. P. tuberculata has 

 its fenestrules very unequal, and its interstices bifur- 

 cate nearly every fourth or fifth fenestrule. 2. M'^Coy's 

 figures and descriptions do not show that the marginal 

 pores encroach on the borders of the fenestrule ; in 

 P. tuberctdata there are raised marginal pores. 3. 

 P. tuberctdata are characterized by the presence of a 

 single row of raised tubercules along the middle of 

 its branching interstices, a feature not observable in 

 M'^Coy's species, and which of itself would mark it 

 as distinct. On account of these differences Dr. and 

 Mr. John Young say that the Scottish Hairmyres 

 species agrees closely in all its important characters 

 with the American P. tuberculata of Prout. § 



As this species will be more frequently met with 

 by the student, it may be advantageous to give the 

 following extracts from Prout's description: — " The 

 Bryozoum (polyzoary) a fan-like expansion ; longitu- 

 dinal rays moderately large, p retty uniform in size, 



* " Transactions of the Academy of Science of St. Louis." 



t Morris's Catalogue of British Fossils. 



% De Koninck on Indian Fossils, jlourn. of Geol. Soc, 

 Nov., 1862. 



§ " Transactions of the Edinburgh Geo. Soc," pt. iii. vol. ii., 

 1874, and Geol. Mag., June, 1874. 



