THE CRETACEOUS FORMATION. 



25 



No. 2. Bairdia Siliqua, nobis. Tab. V, fig. 16 



INCH. 



Length, Jj- 



Var. a. 



INCH. 



Var. /3. 



INCH. 



tV 



Detritus, Charing. 



Height, ^V 



1 



So 



fV 



Chalk, South-East England 



Thickness, J^ 



tV 



-i^ 





Var. a. Detritus, Charing. 



Var. /3. Detritus, Charing. 



— Recent, Tenedos (hairy). i 



— Miocene, Bordeaux. 



CarajMce elongate, sub-triangular, 

 generally smooth, acuminate behind, 

 posteriorly ; ventral nearly straight. 



— Recent, Turin's Island, Bahama. 

 Valves narrov^^, convex, sometimes spined, 

 Dorsal margin strongly arched, slanting off 

 Aiiterior extremity rounded ; posterior acute. 

 Dorsal edge of right (large) valve inverted near the middle ; ventral edge inverted nearly 

 its whole length. 



Dorsal aspect narrow lanceolate ; anterior acutely ovate. 



Variety a (figs. 16 (?, 16/, 16y), about two thirds the length and height of the fore- 

 going, but comparatively more gibbous. Dorsal margin more prominent ; ventral 

 incurved. 



Dorsal aspect elongated oval ; anterior oval. 



Variety |3 (fig. 16 h), about the length of Var. a, very narrow, strongly bent, 

 incurved at the ventral, and arched at the dorsal border. 

 Dorsal aspect narrow lanceolate ; anterior suborbicular. 



We have met with B. Siliqua only in the Chalk and the Detritus. Perfect valves 

 and carapaces of this elegant and fragile species are not easily obtainable from the 

 Chalk. In the Detritus, however, perfect and united valves often occur. A hirsute 

 individual of Variety a occurs at Tenedos.^ Carapaces apparently identical with 

 Var. j3 occur amongst the Fossil Entomosti-aca of Bordeaux, and recent in Turk's 

 Island, Bahama. We may remark that B. Siliqua bears a striking resemblance to 

 Cyris fasciata, Miiller (Entomostraca, p. 53, n. 12, pi. iv, figs. 1-3), and to Cypris 

 ephippiata, Koch (1837, Deutschl. Crustac, Heft 12, t. 1). 



No. 3. Bairdia Harrisiana, 7iobis. Tab. VI, fig. 17 a—f. 



INCH. 



Length, -5^ 



INCH. 



-A' 



Speeton Clay, Yorkshire. 



Height, sV 



-h 



Gault, Leacon Hill. 



Thickness, Jg- 





Detritus, Charing. 



Chalk, Gravesend and Charlton. 



Carboniferous Limestone, East Kilbride. Recent, Mouth of Thames. 



— Manilla (hairy). i 



Carapace elongate, arcuated, varying in the flexuosity of the ventral border. 



1 In Mr. Williamson's Collection. - Specimens of this size are very rare. 



E 



