OABBONIFBBOUB AGK ! !: K M I A N ri:iii<)i>. r.t 



'.I. * 1 II ll! >-|>C( tllllll. I . 



Shell with posterior ear generally larger than the other; hinge without a central cartilage pit; cartilage 



apparently mvupving a aerie* of linear furrow* in a more or leu broad cardinal area. 

 Includes Aticuloiiteten, .VrrV.^.rm, and probably several undefined 1'aUeoaoic genera. 



The A'-i, a/,, / H rt, n f^muii seems to form a kind of transition from the l\<-ih,i<l 

 tn tin- /%///< A r, and may pnsMlily lie distinct frnin them both, though it i- evidently 

 inure closely allied tn the former than the latter. It seems to bear much the some 

 relations to the- typical forms of the Pcctinidas that the PteriniinoB do to the typical 



Pteriil" . 



SUBFAMILY AVICULOPECTININ^E. 

 Genus AVICULOPECTEN, McCor. 



Synon. Arirula, Pecteii, and Melt<ijrina (ip.), of various authors. 



. l. //./,, Mct'oT, Ann. Mag. Nat. HUt. VII, 1851, 171 ; Brit. Pal. FOM. 1852,392. 

 Klym. Arirvla and Pecten. 

 Eiamp. Aviculnjiecttn docent, McCor. 1 



\nimal unknown. Shell inequivalve, more or less inequilateral; straight, or 

 slightly extended obliquely towards the posterior side; anterior ear flattened, 

 smaller than the posterior, sharply and deeply defined, with a notch in the right 

 valve between it and the body of tho shell for the passage of the byssus; 2 

 posterior ear pointed, extending about as far as the margin of the shell, de- 

 fined or not; ligament confined to a narrow 3 facet along the hinge margin; no 

 medial cartilage pit ; muscular impression and pallia! scar as in Pecten, (McCoy.) 



We entirely concur with Prof. McCoy in separating this group of shells both 

 from Ptcria (= Avicida) and Pecten. From the typical species of the latter of 

 these genera, they differ materially in having the cartilage extended along the 

 hinge instead of occupying a mesial pit under the beaks ; they also present the 

 external difference of having the posterior ear larger than the other. From the 

 Ptcrias they arc clearly separated by their more equilateral and less oblique form, 

 edentulous hinge, and the arrangement of the cartilage, as well as by their shell 

 structure. 



Some difference of opinion exists in regard to the family relations of this genus, 

 several authors placing it in the Aviculidce, and others with the Pectinidce. \\ < 



1 In first proposing this genus in the Annals and Mag. Nat. Hist. (VII, 1851, p. 171), Prof. 

 McCoy does not say what species he regards as the type, thongh he figures, as an illustration of the 

 genus, a species (without a name), which seems to be his A. docens ; at any rate it is clearly con- 

 generic with that form. 



1 Judging from Prof. McCoy's figures of Palaeozoic Peclinidx, in hili Synopsis of the Carboniferous 

 Fossils of Ireland, the byssal sinus would seem to be sometimes as strongly defined under the anterior 

 ear of the right, aa well as the left valve, in Aviculopecien ; or there is another genus presenting that 

 character. 



1 Some of our American species have a broad cardinal area, marked with distinct cartilage fur- 

 rows ranging parallel to the hinge line, or sometimes divaricately deflected under the beaks. 



7 June, 1864. 



