1915.] 



NATURAL SCIENCES OF PHILADELPHIA. 



379 



parietal lamella when present is very small, and most specimens lack it. 

 They are very uniform in size and sculpture, in a long series taken. 



Length 8.7, diam. 3.2 mm.; whorls 10; lamellae 1. 

 3 

 3 



3.2 

 3 



3.1 

 3.1 

 3.1 



Holospira campestris cochisei n- subsp. PI. XIV, figs. 6 to 86. 



Similar to campestris, but more slender, with fewer ribs (28 to 40 

 on the penultimate whorl, in the type lot), the intervals wider. 

 Internal lamellae three, the parietal very long and strong. 



Length 10.5, diam. 3.3 mm.; whorls 12; lamellae 3. 



Dragoon Mountains: along the sides of an arroyo or gulley on 

 the mesa within the wide mouth of Tweed Canyon, Station 16; 

 T}T)es No. 112,219, A. N. S. P. Also Stations 17, 19-23, and 27, 

 all in Tweed Canyon. 



The type locality, Station 16 (PI. XIV, figs. 7-7/), is on the sloping 

 sides of the arroyo, which is about 15 feet deep, and meanders across 

 the mesa. Near the mountain the gully deepens to 30-40 feet, the 

 sides become subvertical, and Holospira disappears. The mesa is 

 grassy with some bunches of bear grass. There are some small oaks, 

 juniper, catclaw, etc., in the arroyo. The shells are found under 

 dead sotol and sometimes stones, etc. They reappear just below 

 the igneous dyke near the base of the mountain. Station 17, but do 

 not cross the dyke. Several other arroyos in the same plain were 

 not examined, and there are doubtless many Holospira colonies in 

 the neighborhood. 



Station 19, on the slope near foot of mountain, below the igneous 

 dyke. The shells resemble types of H. c. cochisei except that they 

 are more finely, closely ribbed, ribs 45 to 50 on the penultimate 

 whorl. Ten specimens opened are trilamellate. 



Station 20. Mouth of second ravine west from granitic spur. 



