376 



PROCEEDINGS OF THE ACADEMY OF 



[June, 



Length 12.3, diam. 4 mm.; whorls 12f ; lamellae 1 

 '• 11.5, 

 " 11.3, 

 " 11.2, 

 '' 10.8, 

 " 10, 



Station 18 (PI. XIV, figs. 3, 3a). In the third ravine west of the 

 granitic spur on north side of Tweed Canyon, above a dyke of igneous 

 rock about 50 yards wide. Below this dyke, at Station 17, Holospira 

 campestris cochisei is found. A deep gulley or ''wash" extends 

 from the ravine upon the mesa. The shells at Station 18 are a 

 little more finely ribbed than typical H. danielsi and to that extent 

 approach H. campestris cochisei. Out of 16 opened, 9 shells have 

 3, and 7 shells have two internal lamellae. Measurements follow. 



Station 20 (mouth of the second ravine west of granitic spur, 

 Tweed Canyon). Shells similar to the preceding lot. 



Station 22 (bed of the same ravine several hundred yards above 

 the mouth). Shells similar, but averaging larger, though some 

 are equally small; lamellae one or two. 



Length 12.5, diam. 4 mm.; whorls 12|; ribs 16. 

 " 10.7, " 3.9 " " lU; " 20. 



" 10, " 3.5 " " 111; " 22. 



Specimens from the southeastern part of the upper amphitheatre 

 of Tweed Canyon have only one or two lamellce (parietal and axial), 

 those with one slightly predominating. The parietal lamella is 

 moderate or small when developed. They are also perceptibly 

 stouter in figure than the types, and the number of ribs is, in the 

 main, greater. 



Station 10 (floor of the upper amphitheatre of Tweed Canyon, 

 southeastern branch). Not a favorable station for Holospira, being 

 shaded by a dense growth of shrubs and trees. A few specimens 

 taken have one or two lamellae, and the aperture is built forward 

 further than in the types. Ribs as in the following. 



