BAIRDIA. 



139 



1. Bairdia iNFLATA {Novman). Plate XV, figs. 1 — -i. 



1857. Bairdia subdeltoidea, A. White. Pop. Hist. Brit. Crust., p. 293. 



1849. — — Narrow var. Jones. Entom. Cretaceous Formation of 



England, p. 23 ; and (1856) 

 Tertiary Entom., p. 52.1 



1862. Cythere intlata, Norman. Ann. and Mag. Nat. Hist., vol. ix, p. 49, pi. iii, 



figs. 6—8. 



— SUBDELTOIDEA. Brit. Mus. Cat. Brit. Crust., p. 108 {fide Norman). 

 1868. Bairdia inelata, Brady. Monog. Recent Brit. Ostrac, p. 388, pi. xxvii, 



figs. 9 — 17, and pi. xxxviii, fig. 5. 



Shell tumid ; seen laterally, subrhomboidal in outline, highest in the middle ; height 

 equal to half the length. Anterior extremity obliquely rounded, flattened or somewhat 

 sinuous, bordered occasionally with a flattened spinous lamina ; posterior narrow, rounded' 

 or almost angular, often more or less dentate or spinous ; superior margin forming a 

 flattened arch : inferior straight or slightly waved, bulging more or less at its junction 

 with the anterior margin. Seen from above, ovate, widest in the middle, width nearly 

 equal to the height ; extremities obtusely pointed ; line of junction of the valves waved ; 

 on the ventral smface the left valve much overlapping the right. Surface smooth and 

 pohshed or finely punctate. Muscle-spots arranged in a rosette near the centre of the 

 valve. 



Length, -<f^rd of an inch. 



Recent examples of this fine species exhibit considerable variety of form and, more 

 especially, of surface-sculpture and spinous armature, some being almost perfectly smooth 

 at the extremities, and others strongly margined with spines or dentate lamellae ; some 

 specimens, again, are clothed tow^ards the extremities M'ith numerous long, stiff bristles. 

 Our fossil examples are, however, as yet so few that these variations have not been 

 noticed, but should the species be found to occur in widely distant beds, we may then 

 expect to find varieties of the kind here described. 



Distribution. Recent. — Great Britain. 



Fossil. — Scotland : Raised beach, Oban. 



2. Bairdia (?) Cambrica, 7iov. sp. Plate XIII, figs. 20, 21. 



Right valve, as seen from the side, rhomboidal in outline, greatest width situated in 

 the middle and equal to more than half the length ; anterior extremity gently curved in 



' These references apply to Prof. Rupert Jones's memoranda on the recent shell only ; not at all to his 

 figures or description of the fossil form, which is quite distinct from the present species. 



