DH. T. DAVIDSON ON EECENT BRACHIOPODA. 103 



Subfamily MEGEULiNiE. 



Genus MEGERLIA, King-, 1850. 



This excellent genus was proposed in 1850 by Prof. W. King, at page 145 of Ms 

 monograpli on the " Permian Fossils of England," published by the Palaiontograpliical 

 Society, with the following diagnosis : — " A transversely oblong, uni-areagerous Tere- 

 bratulidia. TJmhone very slightly projecting. Fissure or foramen large, emarginate, 

 and situated in the centre of the area. Cardinal muscular fulcrum excavated. Zoop 

 somewhat quadrate ; confined to the posterior half of the shell ; attached posteriorly to 

 the crural base, and anteriorly to the medio-longitudinal plate. Inner surface of valves 

 radiately pimpled. Punctures large. Type Anomia trimcata, Gmelin." 



We are acquainted with two recognized and one uncertain recent species, viz. : — 



Megerlia truncata, Linne, sp., = var. monstruosa, Scacchi. 

 Megei'lia (?) {Ismenia) sanguinea, Chemnitz, sp. 

 Megerlia Willemoesi, Davidson. Uncertain species. 



As the generic characters have been fully given under Megerlia truncata, they need 

 not be here repeated. 



Mr. Dall, in his Catalogue of the E-ecent Species of the Class Brachiopoda, published in 

 the Proceedings of the Academy of Natural Sciences of Philadelphia, pp. 186 and 187, 

 1873, groups the genus Megerlia into two sections : — 



Section A (Megerlia). Lateral loops closed; shell transverse, sculptured. 



1. Megerlia truncata, Linne. 



Section B (Ismenia). Lateral loops open ; shell more or less swollen, ovate, smooth. 



2. Megerlia Jeffreysi, Dall.* 



3. Megerlia sanguinea, Chemnitz. 



The loop, as shown by Prof. E. Deslongchamps, undergoes certain modifications during 

 its different stages of development. In 1870 Mr. Dall retained the Anomia sanguinea, 

 Chemnitz, as generically distinct from Megerlia truncata, and placed it in the genus 

 Ismenia, but in 1873 he regarded it as representing a section of Megerlia. 



Section A. 



61. Megerllv truncata, Linne, sp. (Plate XIX. figs. 11-20.) 



Anomia truncata, Linne, Syst. Nat. ed. duodecima reformata, p. 11.52, 1767; Andrea, Lettres ecrites 

 de la Suisse, tab. 1. figs, d, e, 1763. 



Anomia disculus, Pallas, Misc. Zool. p. 184, t. 14. fig. 1, 1766. 



Anomie, fig. b, g, Davila, Cat. Syst. et Raisonne des Curiosites de la Nature, pi. xx. 1867. 



Anomia truncata, Chemnitz, Neues syst. Conch.-Cab. vol. viii. p. 90, tab. 77. fig. 701, 1785 ; Born, 

 Mus. p. 118, tab. 6. fig. 14, 1778; Gmelin, ed. Linne's Syst. Nat. p. 3343, 1788. 



* [See page 113 of this monograph, where Dr. Davidson is informed by Mr. Dall that the shell he first named 

 Frenula Jeffreysi, and afterwards described as Ismenia Jeffreysi, is^ the young of Laqueus californicus, var. van- 

 touverinds. — A. C] 



