﻿BIVALVIA. 



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Mactra arcuata. Crag Moll., vol. ii, p. 243, Tab. XXIII, fig. 5. 



Localities. Cor. Crag, Sutton, Ramsholt, and near Orford. Red Crag, Walton, Sutton, 

 Bawdsey. Fluvio-marine Crag, Yarn Hill and Postvvick. 



This shell has recently been found at Postvvick by Mr. Reeve, and some young 

 specimens from Yarn Hill were sent me by Messrs. Crowfoot and Dowson. 



In Mr. Jeffreys' list (appended to Mr. Prestwich's paper) M. arcuata is given as a var. 

 of M. glauca, from which opinion I dissent. There appears to me a greater difference 

 between glauca and arcuata than there is between glauca and stultorum, which are both 

 recent forms. M. arcuata is only known to me as a fossil. 



Mactra artopta. Crag Moll., vol. ii, p. 244, Tab. XXIII, fig. 4. 



This is at present restricted in England to the Cor. Crag, and there it is rare to my 

 researches. It may probably be referred to Mactra podolica, Eichw., in Homes' ' Vienna 

 Foss./ vol. ii, p. 62, Tab. VIII, figs. 1 — 8, where several varieties are figured. Mactra 

 deltoides, Dubois, ' Voth. Pod., 5 Tab. IV, figs. 5, 6, may also be the same species ; but 

 semisulcata is quite distinct. M. artopta is not known to me as living species. It is placed 

 by Mr. Jeffreys in his list to Mr. Prestwich's Cor. Crag paper as another variety of 

 glauca, but from that I dissent. 



Lutraria elliptic a, Lamarck. Crag Moll., vol. ii, p. 251, Tab. XXIV, fig. 1. 



Supplement, Tab. X, fig. 19. 



Localities. Cor. Crag, Ramsholt, Sutton, and near Orford. Red Crag, Sutton. 



In f Brit. Conch.,' vol. ii, p. 431, Lutraria ohlonga is said to occur in the Coralline 

 Crag, and the specimen now figured (which is from my collection in the British Museum) 

 has that name written by Mr. Jeffreys on the back of the tablet, and he has intro- 

 duced the name in his list to Mr. Prestwich's Cor. Crag paper. I have in consequence 

 had the specimen in question figured. It was included with my other specimens as a 

 variety of elliptica, which I still believe it to be, and have in consequence retained it under 

 that name. The specimen in question resembles a figure by Dr. Homes, ' Foss. Moll. 

 Wien,' PI. V, fig. 7 a — c, which he gives as a variety of oblonga, but which M. Cha. 

 Mayer has considered a distinct species under the name of Lutraria Hornesii (' Moll. Tert. 

 du Mus. Zurich/ p. 52, fig. 47, 1867). 

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