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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



the lunule and escutcheon* especially the former. To be more 

 exact, that part of the shell bordering the hinge line is very 

 variable as to extent, ribbing, etc. Ribbing, at the lunule, 

 may cease abruptly, leaving a space which is somewhat convex, 

 and more or less obliquely verrucose, and which may be 

 divided by one or more fissures which are due to the continuance 

 of the growth lines ; or this area may be obviously ribless, or 

 resemble one broad flattened rib, or may be occupied by 

 several obscure ribs. In quite a number of instances it is most 

 difficult to decide as to the enumeration of the ribs in this 

 portion of the shell, and an element of uncertainty is introduced. 



Table III. 



Number of ribs in 300 Bardsea cockles (total population of area examined). 

 Length range 0-98 to 3-67 cm. 8.8.1919. 



No. of ribs. 



No. of cockles. 



20 



4 



21 



13 



22 



53 



23 



91 



24 



74 



25 



44 



26 



16 



27 



5 





Total ... 300 



* Cooke, H. H., " Molluscs," Camb. Nat. Hist. 1895. 



