British Warblers. 57 



arranged spines on ilf urex tenuispinosus Sam. (commonly called Venus's 



comb) render it an extremely 



interesting and delicate object. 



M. Scorpio is remarkable for the 



dilated apices of its fronds ; M. 



radix, for its [fine black short 



spines ; M. regius, for its bril- 

 liant crimson-coloured aperture; 



M. cervicornu, for the forked 



points of its larger fronds ; M, 



palma-rosa, for the delicately 



tinted tips of its finely toothed 



fronds ; and M. haust^llum, for 



its uncommonly lengthened ca- 

 nal. These are mostly tropical 



species ; but the genus is found in all countries : it is marine, and is'na- 



turally furnished with an epidermis, though this is commonly cleaned off' 



before these shells come into the market. 



" Of fossil species of ikfurex there are also many, generally ^belonging 

 to the tertiary beds. 



" There is a circumstance of unusual interest to be observed in the 

 manner in which the animal increases the size of its shell, and which shows 

 most admirably the regularity and beauty of the laws of nature, and directs 

 the mind to the contemplation^of the wisdom and power of the Creator, 

 who alone could teach these little animals how to construct a habitation 

 so perfectly adapted to their circumstances and situation. It will be ob- 

 served, that each periodical increase of these shells, consists of a piece 

 which surrounds about a third part, or less, of the lower portion of the 

 last volution already formed, which portion is always terminated by a varix, 

 which is more or less muricated and even spinose j it is obvious that these 

 murications or spines must be in the way of the future increase of the 

 shells, unless they could be removed from that part which it is intended to 

 cover ; the animal, therefore, is furnished with the means, probably by a 

 solvent liquor, of eating away the lower part of these spines, so that they 

 become detached, and fall off^ by the time that he is ready to form his new 

 inner lip upon the space which they occupy, thus forming a comparatively 

 smooth and even surface, on which it is to spread the testaceous matter, 

 of which the addition to his building is composed." 



Clausilia (clausus, closed ; from a little elastic shelly bone, whose func- 

 tion appears to be to close up the aperture when the animal has with- 

 drawn itself within the shell) ; three species. " This genus, which is 

 terrestrial, consists wholly of small shells, the largest species we know 

 scarcely exceeding an inch in length. Several of the species are common 

 in this country ; in the southern parts of Europe, particularly the islands 

 of the Mediterranean, they appear to abound to profusion." 



Sweety Robert, F. L. S., Author of various Botanical Periodicals, &c. : The 

 British Warblers. Being an Account of the Genus Sylvia, illustrated by 

 beautifully coloured Figures, taken from living specimens in the Author's 

 Collection. The Drawings by E. D. Smith. London. 8vo. Nos. I. to III. 

 This little work is so far valuable, as it makes us intimately acquainted 

 with a genus of songsters which, however much admired in our groves and 

 thickets during the midsummer months, yet, from their retired habits during 

 their annual visit, are not readily distinguished, and never before have been 

 so familiarly described. Mr. Sweet has already described the Sylvia rube- 

 tra, the furze-chat ; S. Phcenicurus, the redstart ; S. Luscinia, the nightin- 

 gale ; S. hortensis, the greater pettichaps ; S. cinerea, the larger white- 

 throat; S. Trochilus, the yellow willow-wren; S. hippolais, the lesser 

 pettichaps; S. sylviella, the lesser white-throat ; S. atricapilla, the black-cap ; 



