78 



THE NAUTILUS. 



ternal folds or callus. There is a strong, deeply entering diag- 

 onal parietal lamella, a smaller one below it; columella termin- 

 ating in a spirally entering lamella. 



Length 8, cliam. 4.1, length of aperture 5.1 mm. (fig. d, 

 apex lost). 



Panama City and Paitilla, near the city, collected by James 

 Zetek, 1917. Also Taboga Island. 



This species stands near P. tr/plicata (Anton) and P. acuta 

 (Orb.) both of which have similar teeth. It is, however, de- 

 cidedly narrower than the first, wider than the second, so that 

 while I hesitate to add another species to this genus, it appears 

 that none of those described will receive It. Phytia rhoadsi 

 (Pils. ), described as a Marinula, and P. setifer (Caop. ) are more 

 northern species, the former somewhat related to P. brevispira. 

 In this species the aperture is longer than the spire, as in Mari- 

 nula, but the other characters are decidedly those of Phytia 

 (Alexia). 



PLANORBIS ISTHMICUS, n. sp. 



The shell is compressed, the thickness 

 about one-third of the diameter, thin, very 

 pale brown, somewhat transparent, glossy. 

 Concavity of the right side showing three 

 whorls and a central pit, that of left side 

 shallow, showing 4 whorls, the last 

 whorl more convex near the sutures, 

 rounded peripherally, not deflected to- 

 wards the left near the aperture. Sculp- 

 ture of fine growth-lines, very distinctly 

 decussated by fine spiral lines on the inner 

 whorls, the spirals weak, in part obsolete, 

 on the last whorl. The aperture is ob- 

 lique, heart-shaped, the lip thin. 



Diam. 10.5, alt. 3.7 mm. 



Panama City, in Chinese wells. Col- 

 lected by James Zetek, Sept., 1918. 



Planorbis liebmanni Phil., maya and 

 orbiculus Morel., are flatter shells, with 

 the spire wider. P. boucardianus Prest. has a more oblique 



