in the West of Ireland. 365 



to nearly two-thirds of the length ; extremities rounded ; 

 superior margin very boldly arched, inferior straight or 

 slightly sinuated in the middle. Seen from above, broadly 

 ovate, greatest width near the middle, subacuminate in front, 

 broadly rounded behind ; width equal to nearly three-fourths 

 of the length. Shell-surface closely and largely punctate, 

 clothed, but not very thickly, with short appressed hairs. 

 Colour yellowish brown. Length -^ inch. 

 Hah. In the Mullingar Canal, Dublin, and dredged (one 

 example) in Dublin Bay, in 3-4 fathoms water. 



The only other localities in which this very distinct and fine 

 species has hitherto been noticed in a recent state are in the 

 rivers Maas and Scheldt in Holland, and in the river Ouse, near 

 Lynn, Norfolk (Ann. & Mag. Nat. Hist. ser. 4. vol. iii. p. 45) ; 

 it is, however, abundant in the fluviatile clays of Hornsea, in 

 Yorkshire. 



The occurrence of this species in several cases in marine or 

 estuarine situations and in company with truly marine species 

 is remarkable. 



Genus Aglaia, Brady. 

 Aglaia comjjlanata, no v. sp. PI. XX. figs. 4, 5. 



Carapace, as seen from the side, oblong, subreniform, highest 

 about the middle ; greatest height equal to less than half 

 the length ; extremities rounded ; superior margin evenly 

 but slightly arched, inferior almost straight. Seen from 

 above, compressed ovate, extremities pointed; greatest 

 width in the middle, and not much exceeding one-fourth of 

 the length. Surface of the valves smooth, bearing a few 

 short scattered hairs ; shell thin and fragile. Lucid spots 

 arranged in an irregular rosette. Length 4^ inch. 



Hob. Westport Bay, 4 fathoms. 



The genus Aglaia was proposed by one of the present writers, 

 in a French publication (' Les Fonds de la Mer ') for the recep- 

 tion of a Mediterranean species very similar to A. complanata 

 in general characters, and exhibiting peculiarities of anatomical 

 structure which distinctly separated it from any established 

 genus. We have had no opportunity of examining the animal 

 of A. complanata. 



Genus Baiedia, M'Coy. 

 JSairdiaftdva, Brady. PI. XVIII. figs. 1-4. 

 Bairdia fidva, Brady, Monog. Kecent Brit. Ostrac. p. 474, pi. 28. fig. 21. 

 Carapace compressed ; as seen from the side, subreniform, 

 rather higher in front than behind ; greatest height near the 



