428 MR. L. RICHARDSON & MR. J. F. WALKER [NOV. I907, 



the result. The beak is incurved, and pierced by a small round 

 foramen. The beak-ridges are concave. The dorsal valve slopes 

 inwards, forming a deep median sinus, which does not quite extend 

 to the umbo of the valve. The hinge-line is slightly curved, and 

 there is a small deltidium in two pieces. 



Remarks. — Oppel, in his ' Juraformation ' (p. 495), states that 

 A. Mandelslohi resembles fig. 12, pi. iv, of Davidson's ' Brachiopoda.' 

 He also refers to Terebratula [Aulacothyris'] impressa. This shows 

 that he based his description of the species on a young shell : the 

 adult specimens are more like fig. 17 of Davidson. He cites as 

 localities the Stuifen and INrpf bei Bopfingen (Swabia) and Egg, 

 near Aarau (Switzerland). 



Quenstedt figures an adult shell, giving as locality, Achdorf- 

 an-der Wutach (Baden), and says that the form is found in the 

 Fariems-Schichten, below the Macrocephalus-Bed in the Brauner 

 Jura, e. 



In the top-bed of the Lower Limestone (Murchisonice), and there- 

 fore immediately below the Pea-Grit proper, are several species of 

 Aulacothyris. The narrowest has been identified by Mr. Charles 

 Upton with A. alveata (Quenstedt). The other two are broader, and 

 possess other additional differences. The middle form, however, is 

 that nearest to A. Mandelslohi (Oppel). The specimens found by 

 one of us (J. F. W.) in the Eullers'-Earth Rock near Erome 

 (Somerset) have the same roof-like ventral valve; but the ridges 

 are not so sharp, and the dorsal valve has a shallower sulcus than 

 the specimens from the Doul ting-Bridge and Earmcombe Quarries. 



DlCTYOTHYRIS STJBRETICULATA (Douville). 



1886. ' Sur quelques Brachiopodes du Terrain jurassique ' Extrait du Bull. Soc. 



des Sci. hist. & nat. de l'Yonne, 2d semestre, 1885 (Auxerre, 1886). 

 Syn. Terebratula reticulata, Sowerby, 1823, 'Mineral Conchology ' vol. iv, p. 8 & 



pi. cccxii, figs. 5-6. 

 Terebratula coarctata, var. reticulata, Sow. ; Davidson, ' Monogr. Brit. Foss. 



Brach.' Suppl. (Palaeont. Soc.) vol. iv, 1877, pp. 143-45. 

 Non Terebratula reticulata, Smith, ' Strata identified by Organized Fossils ' 1816- 



19, pi. xxx [?] fig. 10 ; & ' Stratigraphical System of Organized Fossils ' 



1817, p. 83. 



In 1811 Parkinson called the Bradford-Clay Dictyothyris, Tere- 

 bratula coarctata; in 1816-19 William Smith named it Terebratula 

 reticulata. Sowerby, according to Douville, 



' reconnaissant l'identite des deux especes reprenait le nom de Parkinson qui 

 etait phis ancien, mais appliquait le nom de T. reticulata a une forme voisine 

 et d'un niveau different.' 



Davidson, however, does not explain the employment of both names 

 by Sowerby in quite the same way as Douville ; but, in any case, 

 he did not think that the differences pointed out by Sowerby 

 were ' sufficiently constant to authorize the proposed separation.' 

 He therefore united them (op. cit. pp. 59-60), using Parkinson's 

 name. 



Smith's Terebratula reticulata is the same as Parkinson's T. coarc- 

 tata. But Sowerby's T. reticulata, which he only hesitatingly 



