134 CALIFORNIA ACADEMY OF SCIENCES. 



that, to some extent, there are corresponding local varia- 

 tions in those of North and South America, probably 

 caused by their environments, and not proving their 

 identity. This is alluded to by Dr. Dall as " remarkably 

 similar effects produced by similar environments acting 

 upon plastic forms of the same genetic history." This 

 can hardly apply to the very different climate, vegetation, 

 etc., of Costa Rica, but may account for the similarities 

 in the shells of North and South America. 



In studvincr the variations in the forms of Bulimulus on 



■J o 



the peninsula, anyone must be struck by the numerous 

 characteristics of specific and even generic value which 

 more or less connect them all, and yet divide them into 

 groups so that they appear separable into divisions as ex- 

 treme as almost one for each species. Still they are so 

 linked together that similar characters of less importance 

 connect shells of evidentl}^ distinct genera, and it becomes 

 difficult to decide what to call specific and what generic. 

 Further knowledge of the animals will probably unravel 

 these difficult problems. 



But now, as we look at characters of the shell alone, 

 we find it hard to separate many of the forms specifically 

 because there are so many intermediate specimens. Thus 

 a form from the Sierra El Taste (Meadow Mountains), 

 in the central ridge north of Cape St. Lucas, has char- 

 acters like those of {i) B.vegetus, {2)B. cxcelsns, (3) B. 

 spirifer and (4) B . nioiitezunia (as they were first described 

 in this order), and I therefore call it variety vegexspiza. 

 With the whiteness of No. i, they have the form of No. 2, 

 the fold on columella of No. 3 and the cross-striation of 

 No. 4. (Dall has named this B . ^allidior x-ax . striatula.) 



One of this form was mentioned by me as from Sierra 

 Laguna, in a former article, p. 210, and Dall states that 

 it is common on some of the islands. There is also in 



