KNOWN SPECIES OF MARINE OSTRACODA. 365 



This appears to be a very distinct species, characterized chiefly by the brown hirsute 

 carapace, rounded form of the valves, and the compressed oval outline as seen from 

 above or below. I have a single valve from Honduras which is probably referable to 

 the same species, but is rather intermediate in form between it and B. amygdaloides. 



5. Bairdia subdeltoidea. Von Miinster. (PI. LVII. fig. 8, a-h.) 

 Cythere subdeltoidea, Von Miinster, 1830, Jahrbuch fiir Mineralogie, p. 64. 

 Bairdia subdeltoidea, Jones, 1849, Entom. of Cretaceous Formation, &c., p. 2.3, pi. 5. fig. 15, a-f. 



Bosquet, 1852, Entom. Fossiles des Terrains Tertiaires de la France, p. 29, pi. 1. fig. 13, a-d. 



Jones, 1856, Entom. of Tertiary Formation, p. 52, pi. 4. figs. 2 a, 2b, Z; pi. 6. figs. \ a, I b, 2. 



Egger, 1858, Ostrakoden der Miocan-Schichten, p. 5, t. 1. fig. 1, a-c. Speyer, 1863, Ostra- 



coden der Casseler-Tertiarbildungen, p. 43, t. 1. fig. 5, a-c (right valve), and B. oviformis, ib. 



fig. 6, a-c (left valve). 



Carapace triangular or subtriangular, convex. The left valve is larger and much less 

 angular than the right; its ventral margin arched (sometimes flattened) ; dorsal margin 

 inverted so as to overlap the opposite valve, broad and obliquely rounded in front, 

 more or less produced, tapering, or beaked behind. The right valve is narrower, its 

 dorsal border truncate in the middle ; the ventral border sinuated and having a well- 

 marked convex protuberance on the anterior third, strongly beaked posteriorly, broad 

 and obliquely convex anteriorly : both extremities are often produced, in old specimens, 

 into flattened, denticulate lamellae ; the dorsal edge is slightly inverted at its anterior 

 and posterior thirds. Dorsal aspect oval or subrhomboid. End view broadly ovate or 

 suborbicular. Lucid spots arranged in a rosette, but seldom so regular as in the pre- 

 ceding species. Surface of the valves smooth, often finely punctate, milk-white or 

 pellucid with cloudy patches. The older specimens are mostly quite opaque. 



Length -ioS^ in. (1-27--846 mm.). 



Hab. Australia, West Indies, Turk's Island, Crete (360 fathoms, Capt. Spratt), 

 Serpho {Capt. Spratt). 



This species is very widely distributed both in the fossil and recent state ; and there 

 are a large number of varieties which appear to be fairly referable to it, being connected 

 by a perfect gradation of intermediate forms. The surface-markings are very much 

 dependent upon age, young specimens being generally pellucid, smooth, and free from 

 hairiness or pittings ; adults milk-white in colour, often punctate or slightly pubescent ; 

 while old specimens are more rugged in aspect, their punctuation obsolete, and the 

 extremities occasionally developed into dentated laminae. Besides these various condi- 

 tions, there are doubtless many varieties resulting from habitat, &c. I do not feel sure 

 that the form described by the Rev. A. M. Norman ' as Cythere (Bairdia) inflata is 

 properly separable from B. subdeltoidea, though its much narrower form renders it, at 

 least, a very distinct variety. Some examples of this form (B. inflata), dredged by 



' Annals and Magazine of Natural History, 3rd series, vol. is. plate 3. figs. 6, 7, 8. 



