CHONDRIN^I OF THE PYRENEAN CENTER. 27 



10; length 4.7, diam. 2.5 mm., 6% whorls. Another of the 

 same lot is 5.3 mm. long, with 7 whorls. 



Series of C. bigorriensis. 



The forms of this eminently Pyrenean and Spanish series 

 have often been referred to C. megacheilos of northern Italy, 

 on account of their strong teeth and lip ; yet the relationship 

 appears to be an indirect one, through a common ancestry in 

 the avenacea, stock. The series, while natural enough, is here 

 segregated from the avenacea, series rather as a matter of con- 

 venience in treating the numerous forms than because of any 

 important structural features. However, the lip is usually 

 thickened within. 



The various varieties of P. megacheilos described by Des 

 Moulins and Moquin-Tandon belong to the present group of 

 species and races. P. megacheilos var. rufula Moq., Moll. Fr., 

 p. 354, with the " shell reddish, more or less pale, Saint Sau- 

 veur, ' ' has not been recognized by subsequent authors, though 

 doubtless known under some other name. 



They may naturally be considered under these geographic 

 groups : 



a. Species of the Pyrenees, Catalonia and adjacent prov- 

 inces of Spain, no. 9 to 20. 



&. Species of central Spain, no. 21. 



c. Species of northern Spain, no. 22,' 23. 



d. Species of Portugal, Cadiz and Morocco, no. 24 to 26. 



e. Species of Algeria, no. 27, 28. 



The group (a) of the Pyrenees and Catalonia is intricate, 

 containing many forms which have not been figured or de- 

 scribed in comparative terms, and which are scarcely known 

 outside of the collections of their describers. A table giving 

 some of the main characters is given as an aid to identification 

 of species. The Algerian species also are known by the orig- 

 inal account only. The few forms recorded up to this time 

 from northern and western Spain, Portugal and Morocco are 

 better understood. 



