INSTITUTE OF SCIENCE, PHILADELPHIA. I43 



Subgenus Pterorhytis Conrad. 

 Cerostoma Conrad, Journ. Acad. Nat. Sci. Phila. vii. p. 263, 1837. 

 Pterorytis Conrad, Proc. Acad. Nat. Sci. Phila. 1862, p. 560. 



This subgenus was first described by Conrad with the type M. (C.) Nuttallii, 

 a recent species from Cahfornia. Agassiz in his Nomenclator credits Latreille 

 with a Lepidopterous genus of the same name of the date of 1802, which is 

 probably the reason why Mr. Conrad proposed a new name in 1862 for his 

 genus. As it is commonly admitted that naturalists should reject a name 

 already used in another department of systematic zoology, it does not become 

 necessary for us to investigate the standing of Latreille's name before adopt- 

 ing the second name of Conrad. 



Murex (Pterorhytis) umbrifer Conrad. 

 Murex umbrifer Coma.d., Foss. Shi. Tert. Form., p. 17, pi. 3, fig. i, 1832 ; Emmons, Rep. 



Geol. N. Car., p. 247, fig. 104s, 1858. 

 M. {Pterorhytis) umbrifer Conrad, Am. Journ. Concli. iv. p. 64, pi. 5, fig. 7, 1868. 

 Cerosto7na umbrifer Tuomey & Holmes, Pleioc. Fos. S. C, p. 141 (not pi. 28, fig. 14), 1856. 



Not Murex sexcostata Emmons, op. cit. p. 248, fig. 106, as averred by Conrad, Proc. 

 Acad. Nat. Sci. 1862, p. 560. 



Miocene of Virginia at Yorktown and Day's Point on the James River 

 (Conrad), and of North Carolina on the Cape Fear River (Emmons). 



Two species have been confused by Mr. Conrad and others under this 

 name. The original wnbrifer has " six prominent recurved foliated ribs, " 

 according to Mr. Conrad's figures and subgeneric and specific diagnoses. 

 With this has been confounded another species, M. {P) Conradi Dall, which 

 has but four, ribs or varices, and still another which has six spiral ribs and 

 only three varices, M. sexcostata Emmons {= M. rufus Lam.). Although 

 neither species has yet been found in the Floridian Tertiary, it has seemed 

 best to clear up the confusion here. 



Murex (Pterorhytis) Conradi Dall. 



Plate 12, figure 11. 



Cerostoma umbrifer Tuomey & Holmes, Pleioc. Fos. S. C, expl. pi. 28, fig. 14, 1856 ; 



text, p. 141, exc/us. 



Miocene of St. Mary's River, Maryland (Clark), and of South Carolina at 

 Goose Creek. 



This fine species has, like most of the species of this genus, only four 

 varices. The spire is much shorter than in M. umbrifer and the form of the 

 varices is different. Tuomey and Holmes have figured a broken specimen 

 under the name of umbrifer, though they give as diagnostic " six foliated re- 

 flected laminse," when their specimen had only four ; and this may have been 

 in Conrad's mind when, in his last description of umbrifer in 1868, he allowed 

 it " four lamelliform ribs," while his figure shows six ! 



