03 



but has considerably perplexed the naturalists to whom I 

 have shown it, and will probably be made the type of a new 

 genus Bi issus lyrifer I have found very common in the 

 Clyde, at from ten to thirty fathoms depth, in mud. Not sus- 

 pecting the estimation in which it is held on the score of 

 rarity, I took little pains to preserve specimens ; and was 

 much surprised at being recently told that only four in- 

 dividuals are known to exist in cabinets, besides the two 

 in this Institution, which are of my procuring. In the 

 Zoophyta, I will only occupy your time with one remark- 

 able species, and of it I can only show you a fragment, 

 having sent my perfect specimen, thirty inches in length, 

 to the British Museum. 



After quoting all that has been said of it by authors, 

 Professor Forbes states that Cuvier constituted the genus 

 Pavonaria for itsreception ; that the genus appears to be 

 well founded, and that it will accordingly stand as Pavo- 

 naria quadrangularis. 



In the report of his researches in the iEgean Sea, 

 he has given very interesting remarks upon the zones 

 of depth inhabited by the various species of mollusca, 

 with reference to the bearing of this subject upon geo- 

 logy ; and also states his opinion, that where the same 

 species is common to the Mediterranean and North Sea, it 

 occupies a lower depth in the former. As far as my 

 opportunities of observation have extended, they do not 

 confirm this rule. It may hold good with regard to certain 

 species ; but by far the greater number appear to frequent 

 about the same depth in both localities ; and some I have 

 found inhabiting deeper water upon our own coasts than 

 in the Mediterranean. 



The eminent naturalist above quoted has come to the con- 

 clusion that the zero of animal life in the Mediterranean is at 

 the depth of aboutSOO fathoms. The comparative shallowness 

 of the British seas does not afford the opportunity of throw- 



