56 



AURICITLlDiE. 



appeared to various writers at different times the type of a new 

 genus. The shell, like several other Aurimlidce, has the pecu- 

 liarity of being destitute of the interior septa in the upper 

 whorls, a peculiarity already observed by Chemnitz. 



The formation of the umbilicus is extremely different in the 

 various species ; in several, which at the same time are distin- 

 guished by a more or less triangular shape, it is compressed so 

 as to form only an impressed transverse furrow ; in other species 

 it is perfectly closed, in the remaining ones more or less open. 

 By this difference the known species may be divided in the 

 following manner : — 



A. Umbilicus transversely rimate § 1. No. 1- 5 



B. Umbilicus rather closed § 2. - 6-8 



C. Openly perforated or umbilicated § 3. - 9-35 



D. Doubtful species § 4. _ 36-37 



§ 1. Umbilicus forming a basal impressed furrow. 



1. Pythia tbigona. 



Shell slightly and elongately rimate transversely, much com- 

 pressed, triangular, granularly striated, horn-coloured yellowish, 

 crowdedly spotted and marbled with ehestnut-brown ; spire 

 conoidal, rather pointed, angulated on both sides ; varices pale, 

 bordered with brown ; suture linear ; whorls ten, rather flat, the 

 last higher than the spire, very much dilated, sharply keeled on 

 the side opposite to the aperture, angulated at its base ; aper- 

 ture rather semicircular, obliquely effused ; parietal plaits three, 

 the upper large, flexuosely triangular, the second thick, entering 

 downwards, the third smaller, approximate to the second ; colu- 

 mellar plait compressed, oblique, quite marginal; peristome 

 widely expanded and reflexed, right margin bearing a deeply 

 placed white callus, with five unequal teeth ; eolumellar margin 

 dilated, flattened, spreading. Length 18, greatest breadth 24, 

 least breadth 12 mill. 



Scarabus trigonus, Troschelin Wiegm. Arch. 1838, i. p. 207. pi. 4. 



I* O. 



Reeve in Ann, $ Mag. N. H. ix. p. 219. pi. 4. £ 2, et Conch. 



Sgst. ii. pi. 183. f. 2. 

 Mister, Auric, p. 10. t. 1. f. 6. 



A. Adams and Reeve, Voy. Sdmarang, p. 56. pi. 14. f. 12. 

 A. Adams in Proc. Z. &' 1850, p. 148, et in Ann. & Mag. 



N. H. 2 ser. viii. p. 67. 

 Pythia trigona, Mbrch, Cat. Told. p. 37. n. 767. 

 Pfr. Syn. Auric, n. 72 ; Man. Auric, p. 75. 



