Book Notice. 283 



Continental and United States records. It was an unexpected 

 and gratifying occurrence to meet with it at Martin Beck. It 

 should be mentioned that the two specimens found there 

 differ somewhat from the type form described by Van Heurck, 

 the margins of the vah^es in each case being parallel instead of 

 having a median constriction. In other details they are true 

 to type but not so long, their lengths being respectively 4.2 

 and 7.5 c.d.m. instead of 9.5 as indicated by Van Heurck. 

 One c.d.m. = 10 mikrons. Mere length in a diatom is, however, 

 by no means a constant character. The illustration represents- 

 the longer of the two. 



Navicula Alpina (Fig. 2). The only Diatom in the Alga- 

 Flora endorsed ' rare.' As its specific name implies, it is 

 usually met with at a much greater elevation than Martin Beck, 

 which is only about 100 feet above sea-level. 



Navicula ignota (Fig. 4). Of this, Mr. F. W. Mills, who has 

 rendered me signal service with regard to several doubtful 

 points in this paper, states : — ' The Navicula does not appear 

 to be named, as it is not, I think, mentioned in Clun's Nav. Diat. 

 It is shown, however, in Schmidt's Atlas 43/24, without name, 

 although the stauros is there shown slightly more distinctly 

 than in the photo.' I propose to name this provisionally 

 Navicula Danensis. 



Navicula pusilla (Fig. i). The first record for the South- 

 west division of Yorkshire. Although the illustration has been 

 photographed from an imperfect valve, it is, perhaps, on that 

 account the more interesting. During the process of cleaning, 

 the two valves of the frustule had not been separated— this 

 often happens with Diatoms. In this case, one of the apices 

 of the upper valve was broken away and the line of separation 

 distinctly passes through the dots and not between them, show- 

 ing what is known as the ' postage-stamp fracture.' A careful 

 examination of the illustration will clearly show this and assist 

 in the elucidation of an important fact in Diatom structure, 

 although this feature was evident in the original photo-micro- 

 graph, it has been lost owing to the method of reproduction. 



Common British Beetles and Spiders and how to identify them 

 by S. N. Sedgwick, M.A, London ; Charles H. Kelly (62 pp., price 

 1/6 net). This book attempts too much at once. In -13 pages, even with 

 the aid of 13 plates, it is obviously impossible to describe adequately the 

 Beetles and Spiders commonly found in Great Britain, and the publishers 

 would have been well advised to have issued a separate volume for each. 

 The illustrations of beetles are reproduced from photographs of carded 

 specimens, and while this treatment gives a fairly good likeness of the 

 larger, it renders the smaller species as hopeless blurs. The book is 

 lightened by a ' General Description ' containing the information usually 

 repeated in books of this nature, though we do not remember previously 

 reading that ' the glow-worm, like one of the girl-guides, learns "lamp- 

 signalling " in the dark whether to summon a husband or a partner to a 

 rich juicy snail supper.' This seems rather hard on the girl guides ! 



1918 Sept.l. 



