HARDWICKE'S SCIENCE-GOSSIP. 



189 



GEOLOGY. 



The Silurian Species of Glauconome, and 

 a suggested classification of the palaeozoic 

 PoLYZOA, — This was a paper recently read before 

 the Geological Society, by Messrs. G. W. Shrubsole, 

 F.G.S., and G. R. Vine. The authors discussed the 

 history of our knowledge of the genus Glauconome, 

 and especially of the Silurian species. They then 

 characterised the genus, to which they refer only the 

 Bala species formerly regarded as identical with 

 G. disticha, Goldf., but which they describe as 

 G. Sedgwickii, Shrubs. Glauconome disticha, Goldf., 

 from the Wenlock of Dudley, is taken as the type of 

 a new genus Arcanopora. The authors then remarked 

 upon the characters on which the classification of the 

 Polyzoa is founded, drawn from the study of the 

 recent forms, and stated that throughout the Caino- 

 zoic and Mesozoic series no Polyzoa are known which 

 cannot be referred to the recognised groups. Many 

 Palaeozoic forms are in a different case. The orifices 

 seen on the surface are not, in many instances, the 

 mouths of the cells, but those of what the authors 

 call vestibules beneath which the true cell-mouth is 

 concealed. For these types they propose to found a 

 new suborder under the name of Cryptostomata, 

 and characterised by having the zooecia subtubular, 

 or, in section, slightly angular, and the orifice sur- 

 rounded by a vestibule or otherwise concealed. The 

 families referred to this group are the Ceramoporidae, 

 Ptilodictyidce, and Arcanoporidae, 



On TIE Cause of the Depression and Re- 



ELEVATIO.V OF THE LAND DURING THE GLACIAL 



Period. — Mr. T. F. Jamieson, F.G.S., has read a 

 paper on the subject before the above Society. The 

 author commenced by noticing the theory advanced 

 by Adhemar and Croll, according to which the sub- 

 mergence was due to the effect of a polar ice-cap causing 

 a displacement of the earth's centre of gravity, and 

 thereby drawing the ocean towards the ice-covered 

 pole ; he proceeded to show that this theory is 

 opposed to the geological evidence, according to 

 which the amount of submergence has been unequal 

 in adjacent areas and along the same parallels of 

 latitude, showing that the movement has been in the 

 land and not in the sea. The facts of submergence 

 also prove that no such cap of ice could have existed 

 at the time in the northern regions. Sundry other 

 objections were also pointed out. The author then 

 went on to state his own hypothesis, which is to the 

 effect that the depression of the land was caused by 

 the weight of ice laid upon it, and the re-elevation by 

 the disappearance of the ice. The amount of depres- 

 sion would depend partly on the weight of ice and 

 partly on the elasticity or yielding nature of the 

 ground beneath it. He then proceeded to consider 

 what was the weight of ice that probably existed, and 



referred to the elastic and flexible nature of the 

 earth's crust, as evinced by earthquakes, &c. He 

 further considered the relation of time to pressure, 

 and touched upon the probable rate of subsidence, 

 which he supposes to have been very slow and gradual. 

 The recovery of level, he thinks, would also be very 

 gradual, and probably, in most cases, not complete. 

 He next proceeded to show how his hypothesis is 

 borne out by an appeal to geological evidence in 

 various countries, taking England, Ireland, North 

 America, and Greenland as examples. He further 

 pointed out its application to tlie facts connected 

 with the loess beds, Fjord latitudes, and lake-basins, 

 and concluded with some observations on the remark- 

 able connection between glaciation and submergence 

 in all countries. 



"Half-Holiday Handbooks." — This is a series 

 of ninepenny brochures published by Mr. T. Fisher 

 Unwin (late Marshal Japp & Co.), which purport to 

 give an account of the Geology, Botany, and Natural 

 History of various districts favourably situated for 

 holiday excursions. Being familiar with some of the 

 districts mentioned, we have personally tested the 

 accuracy of these Handbooks, and have been agree- 

 ably surprised by their fulness, clearness, and general 

 accuracy. The first is entitled " Geological Rambles 

 around London." "Greenwich and Blackheath;" 

 "Round Tunbridge Wells;" "Round Reigate ; " 

 " Kingston-on-Thames ; " "Dorking and Neighbour- 

 hood ; " "Round Richmond;" "Croydon to the 

 North Downs," &c., are others. All are illustrated 

 by maps, fossils, plants, insects, &c. They are most 

 valuable auxiliaries to a holiday tour, and many a 

 young naturalist will be grateful to their authors and 

 publisher for their publication. 



NOTES AND QUERIES. 



The Cuckoo's Eggs.— In the lists that I have 

 seen of nests in which the cuckoo lays her egg (or 

 eggs, as the case may be), I have never noticed that 

 of the reed warbler {Saltcaria arundinacea) : a day 

 or two ago, however (May 19th), on an island in the 

 river, which had been selected for breeding by 

 several pairs of reed warblers, I found one nest with 

 three eggs " sui generis," and one cuckoo's egg. The 

 cuckoo had been noticed about the island on the pre- 

 ceding day. — G, T. B., Oxford. 



Unexpected Guests. — Some time ago my son 

 brought in some cocoons, which he said he had taken 

 from a thorn hedge. I thought they must be the 

 compact cases of the small eggar moth, and ac- 

 cordingly waited for the emergence of the moths with 

 some pleasure. Judge of my surprise when my 

 cocoons produced, not moths, but bees ! These in- 

 sects have clubbed antennae, and beautiful bordered 

 wings, which give the appearance of having been 

 varnished. I enclose one of the empty cases, in the 

 hope that you will be able to help me to the name 

 of my unexpected guests. — IV. M. C. C. 



