TRANSACTIONS OF WAGNER 



772 



TERTIARY FAUNA OF FLORIDA 



has not been carried so far as to form crura. Coincidently with the existence 

 of the enormous plug in this group, the byssal muscle has been enlarged 

 until it exceeds in section the size of the adductor, above which it is inserted 

 on the surface of the left valve. In Avomia proper and ALuigma, the other 

 features not being greatly modified, we have the byssal muscle divided into 

 several bundles, each producing its separate scar on the upper valve. 



In the form of Carolia, which we are about to describe, we have combined 

 with the single chondrophore of Monia the obsolescent notch and plug, to- 

 gether with the simple adductor scar of Ephippiitm. The sensible but narrow 

 cardinal area of the latter is represented by a broad and conspicuous margin. 

 The lateral edges of the ligamentary scar in the left valve form narrow 

 elevated crura, while the exterior is free from the radiating strije common 

 to all the other forms and resembles that of the smooth Anomias. If these 

 differences be taken as sufficient for establishing a section of the subgenus, 

 the name Wakullina will be used, from Wakulla County, Florida, in which 

 the type specimens were collected. 



The synonymy of this group is in an unsatisfactory condition. The 

 genus Placenta was first named by Da Costa in his Conchology (p. 271, 1776), 

 though, unfortunately, this author not having consistently adopted in this 

 work the Linnean nomenclature, it is not entitled to be cited in synonymy. 

 The name Placenta had been used by Klein in 1734 to designate an Echino- 

 derm, but this author is absolutely without a binomial nomenclature and not 

 entitled to any consideration in discussing systematic questions. Da Costa's 

 name became current among students and was adopted in proper binomial 

 form by Retzius in his well-known dissertation on new genera of shells, pub- 

 lished by his pupil, Phillipson, at Lund in 1788. 



Meanwhile Linne had referred the species to Anon/ia under the name of 

 Anoinia placenta. In an unpublished description of the shells in the ducal 

 cabinet of Portland, Dr. Solander had proposed the name Placuna for the 

 same type, and this was used by Bruguiere on the plates of the unfinished 

 Encyc. Methodique (174, 175, 1792), though with the genuine Placuna he 

 united certain species of Plicatula. Solander's name was also quoted by 

 Humphrey in his Catalogue of the Museum of Calonne (p. 45, 1797), which 

 contained a number of specimens derived from the Portland cabinet. A year 

 or two later Bolten revived the hitherto nonbinomial name of Ephippuun 

 employed by Chemnitz to designate (Conch. Cab., viii., p. 116, 17S5) the 

 saddle-oyster, — he included that as well as Anoniia placenta in his genus 



