306 BULLETIN OF THE 



from Texas, but not rare in West Florida; the P. papyratia of Say (uot of 

 Gould's Inv.) is rare. 



Two other small and apparently rare species exist on the coast, one of which, 

 p. fragilis of Totten, a northern form, has long been considered as Say's spe- 

 cies, although the shell in question does not agree with Say's in measurement, 

 in habitat, or with his description. But being the only one at all well known, 

 and Say's type apparently being lost, it seems to have been supposed that Say's 

 name must apply to it. This error was corrected by Conrad. The other spe- 

 cies (yet undescribed unless it be the undulata of Verrill, which I have not 

 seen) is close to papyratia in size, and chiefly differs in proportions. 



Periploma papyracea (Say em.) Stimpbon. 



Anatina papyratia Say, Journ. Acad. Nat. Sci. Phil., II. p. 314, 1822 ; Binney*8 



Say, p. 104, 1858. 

 Periploma papyracea Conrad, Am. Journ. Conch., II. p. 7.0, pi. iv. fig. 9 (poor) ; 



Ibid., p. 281, pi, XV. fig. 6, 1866. 



Habitat. Station 128, otf Frederikstadt, Santa Cruz, in 180 fms. ; one liv- 

 ing specimen. 



Totten's species is larger, flatter, more equivalve, rounder, aiid those I have 

 seen are destitute of the faint rib extending backward and downward from the 

 beaks. I should have been disposed to consider, from Say's description, that 

 he had under his eyes a very young P. angulifera, in which the discrepancy of 

 the two valves is greater and the rib is strong. But as Conrad has fixed upon 

 the shell which is in our hands, and figured it under Say's name, and there is 

 no means of absolutely settling the question by reference to a type, it seems 

 better to let Conrad's arrangement stand unmodified. 



In this species the siphons are wholly disunited and retractile, the foot 

 very small, clavate; the labial palps enormous, lamellate, and far exceeding 

 in size the single gill on each side. In P. fragilis the palps are smaller, but 

 of similar character, while the gills are proportionally larger and the siphons 

 separate and unequal The prop to the fossette in fragilis is conchologically 

 a step toward Anatina proper ; but the others are without it. 



Gends THRACIA (Leach Ms.) Blainville. 



This genus is a synonym of Rupicola, Fleurian de Bellevue (1802), which is 

 nearly a quarter of a century older, but the name Rupicola was used by Bris- 

 son for a genus of Birds in 1760. Now Brisson did not use the binomial no- 

 menclature in the modern sense, and strictly speaking should have no standing. 

 Nevertheless his generic names are adopted by ornithologists, and on this 

 ground we may consider the name Rupicola preoccupied in a certain sense. It 

 should, however, be rejected entirely, and not used in a subgeneric or sectional 



