ANAPTYCHUS, RHYNCHOL1TES, ETC. 269 



specimen with (Toniatites. Nearly fifty varieties have been 

 described. 



Meyer considered them bivalve shells, and described them 

 under the name of Aptychus ; Deslongchamps with the same im- 

 pression, called them Munsteria ; d'Orbigny thought them plates 

 of cirripedes, and Deshays believed them to be the gizzards of 

 Ammonites ; Coquand compared them with Teudopsis, and they 

 certainly resemble in some degree that genus, as well as Belo- 

 teuthis, Belemnoxepia, etc. 



A. LAMELLOSUS, Park. PL 104, fig. 573. Oxford Clay, Solen- 

 hofen. 



T. LATUS, Brown. PI. 104, fig. 575 a. 



TRIGONELLITES associated with an Ammonite. PL 104, fig. 574. 



Genus ANAPTYCHUS, Oppel. Horny and flexible, in a single 

 piece. 



Associated with the Arietes group of Ammonites. 

 Anaptychus of AMMONITES COSTATUS. PL 104, figs. 515, 576. 



BEAKS OP TETRABRANCHIATES. 



These are found associated with fossil Nautili and occasionally 

 Belemnites, but never with Ammonites. The upper beaks have 

 been described under the name of RHYNCHOLITES, the lower 

 ones- as CONCHORHYNCHUS. 



R. ASTIERIANA, d'Orb. PL 104, fig. 577. 



< 1 . AVIROSTRIS, Bronn. PL 104, fig. 978. 



0. OWENII, Bronn. PL 104, fig. 579. 



PELTARION, Deslongchamps. This was formerly believed to 

 he the mandibular armature of tetrabranchiates, consisting of 

 circular or transversely-oval calcareous plates, with rounded 

 anterior and produced and truncated posterior margins. Through 

 the researches of M. Crosse (Jour, de Conch., 3 ser., xv 57, 

 1875), there is no doubt that these Peltarise are opercula of 

 fossil species of Neritopsis ; they resemble the operculum of the 

 recent N. radula. 



Several species have been described from IT. Lias to Coral- 

 line Rag. 



