considered Zoologically and Geologically. 223 



2. The relative proportions of univalve and bivalve testacea 

 met with would depend on the part of the bed examined, 

 whether its centre or its edge. 



3. The Chitons would scarcely be met with in consequence 

 of their fragility and disorganization after death, though abun- 

 dant on the bed in a living state. 



4. It is probable that a greater number of species would be 

 met with in the fossil than in the recent bed, since the rarity 

 of certain species would seem rather to depend on the paucity 

 of individuals than on other causes ; and as the probability of 

 meeting such would depend on the extent of surface examined, 

 the inspection of a bed of shells high and dry would be more 

 likely to reward our researches than an examination con- 

 ducted in the deep sea by means of the dredge, which must 

 always be partial. 



5. Of the Echinodermata we should probably find the re- 

 mains of sea urchins only ; and as they generally fall in pieces 

 like the Chitons, we should be obliged to determine the spe~ 

 cies from fragments. I may mention that I find good specific 

 characters in the spines alone of our native living species, and 

 no doubt such is also the case with the fossil. 



6. Of Zoophytes we should find only the remains of a few 

 species (having calcareous polypidoms) belonging to the order 

 Ascidioidea. The greater number would probably altogether 

 disappear. 



7. The larger Crustacea being very few, and the smaller 

 very small and fragile, or else unpresentable in such circum- 

 stances, though very numerous living, we should find but few 

 traces of the presence of the tribe. 



8. The testaceous Annelides would remain, the soft tribes 

 altogether disappearing. 



I have drawn up these observations chiefly in the hope of 

 inducing others to present us with similar reviews of the shell- 

 banks of our coast. Geology and zoology will gain as much 

 by inquiring how our marine animals are associated together 

 as by investigating genera and species, though the former sub- 

 ject has as yet been but little attended to in comparison with 

 the latter. 



