288 HAAS: ABIDA AND CHONDRIXA. 



11 mm. high, 3.5 to 4 mm. in diameter; one specimen has a 

 diameter of 4.5 mm. with height of only 8 mm. 



Upon the mountains of the mouth of the Ebro, where C. b. 

 tenuimarginata has been found in recent years, a form lives 

 which can only be compared with the form gigantea of C. b. 

 bigorriensis of Gavarnie. It measures up to 10.5 mm. high 

 with 4.5 mm. diameter, and is notable for the extremely fine 

 striation of the shell and weak structure of the apertural 

 lamellae. Besides the two palatals there are indications of 2 

 supra- and 1 infrapalatal. A specimen from Forat Negre at 

 the Hospitalet del Infant, near Vandellos, Prov. Tarragona, 

 is drawn in pi. 26, fig. 12. 



C. bigorriensis tenuimarginata is known up to this time 

 from the French and Spanish East Pyrenees, the Spanish 

 High Pyrenees, westward to the Rio Salarar in Navarra and 

 the coastal region skirting the Pyrenees south of the mouth of 

 the Ebro. Included in this area lies the isolated mountain 

 mass of Montsech, where a special local race of bigorriensis 

 has been evolved, the C. b. microchilus Bofill, about to be dis- 

 cussed. 



In his treatise "Estudio critico de la Pupa megacheilos 

 Cristofori et Jan y de algunas formas derivadas de ella que 

 viven en Esparia" (Real Sociedad Espanola Hist. Nat., Ma- 

 drid, Tomo Extraordinario, del 50 Aniv., 1921, pp. 309-336, 

 pi. 19), F. Azpeitia treated of the south Pyrenean local races 

 of Abida bigorriensis (which species he considered a local 

 race of C. megacheilos), and investigated the forms gonio- 

 stoma, leptocheilos, adeodati, microchilus, bigorriensis, elon- 

 gatissima, gigantea, juliensis and angulata in their relations 

 to this. His results are almost the same as those to which 

 my own studies have led; only he did not recognize C. bigor- 

 riensis bigorriensis as a local form independent of C. b. tenui- 

 marginata. This was evidently because his research material 

 was from the Aragonian part of the range, whilst A. b. bigor- 

 riensis occurs only in the southern part of these mountains. 

 Having before him no authentic material, he took Pupa micro- 

 chilus Bof. to be merely a small-mouthed form of tenuimargi- 

 nata, whereas I hold it to be the local race characteristic of 

 the Montsech range. 



