THE NAUTILUS. 77 



Compared with P. rhyssa, P. altissima is not only much smaller, 

 but also much flatter, with the aperture consequently narrower and 

 the last whorl less evenly rounded. I have specimens of P. rhyssa 

 from the original locality, collected by Mr. Ashmun ; the species 

 was also found by Prof. Towusend in the White Mountains, at an 

 altitude of about 8,000 feet. 



The following form, also from the White Mountains, seems worth 

 defining : 

 Polygyra rhyssa var. hyporhyssa v. nov. 



Like P. rhyssa in size and form, but umbilicus wider, exposing 

 the penultimate whorl ; sculpture finer, consisting of strke rather than 

 rihlets. Collected by Prof. C. H. T. Townsend on the lower slopes 

 of Sierra Blanca, N. M., above head of Ruidoso Creek, in aspen 

 belt, about 9,500 ft. alt., Aug. 14, 1898. One specimen, diam., 

 max. 15, min. 121, alt. 9 mm. This is clearly a variety of rhyssa, 

 and is not the same as Ball's MS. P. miorhyssa, which appears to 

 me to be a perfectly distinct species. 



NEW PISIDIA. 



BY DR. V. STERKI. 



P. roperi n. sp. 



Mussel rather large, strongly inflated when mature, very little so 

 when young ; oblong to ovoid in outline, margins regularly curved, 

 with no projecting angles (in the adult) ; scutum and scutellum 

 scarcely marked ; beaks moderately posterior, very broad, surface 

 somewhat glossy, with irregular, not sharp, striaj and some strongly 

 marked lines of growth ; color of the dry shell straw to yellowish- 

 horn, often with one to several fine, concentric lines of purple ; shell 

 rather thin, nacre whitish, muscle insertions scarcely marked, hinge 

 comparatively fine and short; cardinal teeth quite small, the right 

 one moderately curved, slightly thickened at the posterior end; the 

 left ones very short ; the inferior slightly angular, truncated or 

 pointed on top, the superior sometimes almost obsolete ; lateral teeth 

 short, small, scarcely projecting into the interior; ligament rather 

 fine. 



Long. 5'5, alt. 4'4, diam. 3.8 (4) mill. 



Long. 4'5, alt. 3'7, diam. 3'0 mill. 



