Reviexvs — B. B. Woodward's Life of the Mollusca. 81 



sharp-pointed teeth, which in those feeding on livififf animals are 

 barbed to retain their prey, while in the Cones the teeth are not 

 only barbed but perforated and connected with poison glands." 



" In habit the Mollusca are far from active, only some of the cuttle- 

 fislies being capable of spasmodic rapid motion, so much so that the 

 term ' sluggish ', borrowed from them, best describes them." (p. 13.) 



Let us now turn to the geological history of the Mollusca. In 

 chapter iii Mr. B. B. Woodward tells us these animals made their 

 appearance very early in the world's history, the more generalized 

 forms preceding the more specialized. In the oldest fossiliferous 

 beds of the Lower Cambrian only a few representatives have been 

 found. These consist of some limpet-like shells {Sce^ieUa, Stenotheca, 

 Platyceras) ; also a tiirreted convolute shell {Itaphistoma), and the 

 remains of two bivalves. 



In the Upper Cambrian further examples of the early Rhipidoglossa 

 are found \]ihirchiso7iia, Cyrtolites, Owenella, and StraparoUma), as 

 well as one {Troclionema) a supposed member of the higher one-gilled 

 section of that sub-oi'der. Already, too, seven species of Cephalopoda 

 had made their appearance, all belonging to the more primitive 

 straight-shelled section of the Nautiloidea. In the succeeding 

 Ordovician epoch Aspidobranch Gastropods predominated ( Cyclonema 

 and top-shells, Turbinidse), and the first Chiton appears {PriscocMton). 

 The Cephalopoda are represented by sixty-five species of Nautiloidea, 

 mostly straight-shelled, but some curved and a few coiled forms. 



Considerable increase in the Mollusca occurs in the Silurian epoch. 

 Members of three families are added to the Grastropods, and of 

 Pelecypods Paloeoconchs were most abundant. Two more Chitons 

 appeared and some doubtful Scaphopods. " The Nautiloidea attained 

 their zenith with about 230 species, among which the coiled were 

 almost as abundant as the other sliell-forms. From that day the 

 group has steadily diminished in numbers, only five species now 

 existing" — probably not so many. 



In the Devonian strata there is a still further increase of the 

 Pelecypoda (Trigonise, Pectinidse, Mytilidce, and many others). 

 The first freshwater mussel, Archanodon Jukesii, appears, closely 

 I'esembling the modern Anodojita (swan mussel) of our ponds and 

 lakes. A true Bentalium and representatives of the more primitive 

 Ammonoidea ( Clymenia) and Goniatites appear in the Devonian 

 epoch. At its close land-snails {Sirophites, Dendropupa, etc.), allied 

 to the chrysalis shells, have been found in the plant-beds of St. John's, 

 New Brunswick. The Coal-measures of the Carboniferous period 

 have yielded some other interesting air-breathing snails (^Dawsonella, 

 etc.), the first brackish-water snail {Anipullaria), a freshwater 

 snail {Physa), and a small land shell (near to Pyramidula), a common 

 form to-day. Many examples of freshwater bivalves (Cardiniida)) 

 were plentiful in the Carboniferous ; the oldest Tectibranch ( CyJindro- 

 bullina) has been obtained, and a highly specialized bivalve {Litlxo- 

 phagiis) that burrows into rock, shell, or coral. 



Although at the close of the Palaeozoic period many of the older 

 genera of bivalves disappeared, at the opening of the Mesozoic period 

 in the Trias a number of others came in. Among them we find 



DECADE VI. — VOL. I. — NO. II. C 



