438 DR. WHEELTON HIND ON NAIADITES IN [A.Ug. 1 894, 



Measures, a fact which was recognized by the late Mr. Salter, who, 

 in a description of Sir William Dawson's shells, Quart. Journ. Geol. 

 Soc. vol. xix. (1863), substituted the names of his newly-erected 

 genera Anthracoptera and Anthracomya for Naiadites, notwith- 

 standing the critical objections raised by the author of the name 

 Naiadites. 



I have been in correspondence with Sir William on the subject, 

 and propose to retain the name Naiadites for the form called 

 Anthracoptera. 



In my paper published in this Journal, vol. xlix. (1893), p. 249, I 

 figured and showed that Salter's Anthracoptera had a striated hinge- 

 plate, a character, the absence of which had been considered to 

 separate the genus Myalina (De Koninck), and in Geol. Mag. 1893, 

 p. 514, I published a note on Myalina crassa, pointing out that 

 there were no anatomical features by which the shells known by 

 that name could be separated from Salter's Anthracoptera, at the 

 same time noting that the septa within the beaks described by 

 J)e Koninck were absent. On looking up De Koninck's original 

 description and figures I find in 1842 (' Descript. des Animaux 

 Fossiles,' p. 125) the following description : — " A l'interieur et 

 immcdiatement au-dessous de ceux-ci [the umbones], une petite lame 

 septiforme, semblable a celle que Ton observe dans certaines especes 

 de Mytilus." The figure given is too imperfect to show these 

 characters. In his more recent work, ' Faune du Calcaire Carboni- 

 fere,' ' he describes the genus and says it is " muni d'une cloison 

 interieure," but the figures, especially figs. 5, 7 and 9, pi. xxix., 

 demonstrate most conclusively that this septum did not exist in 

 them. 



Prof. King (' Permian Fossils,' pi. xiv. figs. 5, 7 & 12) shows 

 shells from the Permian which appear to possess this myophorial 

 septum, to which he gave the names Mytilus squamosus and M. 

 septifer, but in the text he suggests their reference to De Koninck's 

 genus. 



M'Coy (' Brit. Palaeozoic Foss.' p. 492) says, in his description of 

 Myalina, that there is " a triangular septum in the cavity of each 

 beak, paraUel with the plane of the lateral margins, leaving deep slits 

 under the beaks of the cast," but he mentions no specimens from 

 the Carboniferous series. When in the Brussels Museum a few 

 months ago I was unable to see any signs of the septa in De 

 Koninck's specimens, and think it probable that many of his forms 

 will have to be placed with Naiadites, the name Myalina being 

 retained for the septiferous forms from the Permian, and for any 

 which may appear in the Lower Carboniferous series. 



[It has been thought advisable, at the suggestion of the Council 

 and with the assent of the author, to incorporate here the following 

 synonymy of Naiadites. — Ed.] 



1 Ann. Hist. Nat. Musee roy. de Belgique, vol. xi. 1885. 



