1 74- Bibliographical 'Notices. 



show at a glance that the structure is not that ol any 

 Diatom. 



Dictyocha. — In Dr. GwyA JeiFreys's Report on the ' Valo- 

 rous ' Expedition (Proc. Roy. Soc, June 1876, p. 228), there 

 is an account of some Diatoms examined by Professor Dickie, 

 it being mentioned incidentally that along with these " were 

 two Polycystina, namely Dictyocha fibula^ Ehr., and Dicty- 

 ocha gracilis, Ehr." With all deference to Prof. Dickie, I 

 beg leave to point out that the Dictyochidce are neither Dia- 

 toms, as they have been regarded by some writers, nor Poly- 

 cystina as they would now appear to be regarded by others. 

 They are Rhizopods, holding an intermediate place between 

 Thalassicolla on the one hand, and the siliceous sponges on 

 the other ; and hence (as was long ago shown by me) they 

 constitute the true connecting link between the Rhizopods and 

 the Sponges. The basket-shaped framework of the living 

 Dictyocha is never single, but invariably double, the concavi- 

 ties being placed face to face, and the two portions retained in 

 position solely by the sarcode body, which fills and surrounds 

 them. The distinct nucleus may always be seen, in recent 

 specimens, suspended as it were in the middle of the sarcode, 

 half within the boundary line of one framework, half within 

 that of the other. The most remarkable feature, however, of 

 Dictyocha, and the one which at once establishes its alliance 

 with the siliceous sponges, is that every part of the siliceous 

 framework is tubular. 



BIBLIOGEAPHICAL NOTICES. 



The Primaeval World of Switzerland. With 560 Illustrations. By 

 Professor Heer. Edited by James Hetwood, F.R.S. &c. 2 vols. 

 8vo. Longmans & Co.: London, 1876. 



The Geology of England and Wales. By Horace B. Woodward, 

 r.G.S. &c. With coloured Geological Map and numerous wood- 

 cuts. 8vo. Longmans & Co. : London, 1876. 



England and Wales have been said to exhibit an epitome of geology 

 to the student of successive rock-formations and fossiliferous strata. 

 From the oldest and lowest, or nearly lowest, known series of rock- 

 masses, now much altered, to the latest or uppermost deposits cf 

 sea, lake, and river, some representative rock or layer is found in 

 place, indicating period after period of the earth's history, as far as 

 geologists can recognize its terraqueous existence. 



Switzerland also presents an epitome of the geological history of 



