FREE INSTITUTE OF SCIENCE 



1327 



TERTIARY FAUNA OF FLORIDA 



siphons almost wholly united and none of them free. The possession of a byssal 

 groove or developed byssus is also characteristic, as far as known, of only 

 a minority of the European forms and is not reported in the American ones. 

 These facts seem, on the basis of the diagnostic characters, to fully justify the 

 suppression of the subfamily Tapetina of Fischer which I formerly accepted 

 without investigation (see page 552). 



The subgenus Protothaca is the only one which is represented in North 

 American Tertiary beds, and in these only on the Pacific coast, where Paphia 

 {Protothaca) staminea Conrad occurs abundantly in the Miocene and succeed- 

 ing horizons, as well as some other species enumerated by Gabb. 



Genus LIOOYMA Dall. 

 Liocyma Dall, Proc. Bost. Soc. N. Hist., xiii., p. 256, 1870, Venus Auctuosa Gould; Am. 



Journ. Conch., vii., p. 145, 1871 ; Fischer, Man. de Conchy!., p. 1086, 1887. 

 Lyocima Barrois, in Zittel, Traite de Pal., ii., p. 109, 1887. 

 Tapes (sp.) Deshayes, Cat. Conch. Brit. Mus., i., p. 176, 1853. 

 Venus (sp.) Gould, Inv. Mass., p. 87, 1841 ; De Kay, Zool. of N. Y., Moll., p. 220, 1843. 



This animal has two moderately developed siphonal tubes with papillose 

 orifices, the anal shorter than the other when both are extended fully. The 

 tubes are united ; the foot is long and pointed without a byssus or groove, the 

 mantle open ventrally and smooth-edged. The valves are concentrically waved 

 and covered with a thickish vernicose periostracum ; their inner margins are 

 smooth ; the pallial sinus is short and rounded triangular, free below from the 

 pallial line. The lunule is circumscribed by a weak incised line, but there is 

 no defined escutcheon. There are three cardinals in each valve; the posterior 

 left and the anterior right are entire, the others bifid or grooved. The teeth 

 and nymphs are smooth with no trace of any lateral teeth. The general form 

 is ovate or rounded trigonal, with moderate convexity. The coloration is white, 

 pale green, or brown, with no pattern markings. The species are all sinall and 

 confined to the boreal or arctic waters of the northern hemisphere. The genus 

 goes back to the Pliocene in time. Dental formula ^- '°'°'°- . Although in a 



° R. oioioi. 



general way not unlike Paphia in miniature, this little group seems sufficiently 

 distinct to stand as a genus. It is not reported from the Tertiary, but occurs 

 in the Arctic Pleistocene on the Alaskan coast and living in the adjacent seas. 



Genus VENERUPIS Lamarck. 

 Venerupis Lamarck, An. s. Vert., v., p. 506, 1818; Blainville, Man. Mai., i., p. 559. 1825 

 (V. irus L.) ; Payraudeau, Moll, de Corse, p. 35, 1826; Fleming, Brit. An., p. 451, 

 1828; Philippi, Moll. Sicil., ii., p. 20, 1844. 



