20 PKOF. T. E. JONES ON SOME PALEOZOIC OSTEACODA 



border gently curved and ciliated (PI. III. figs. 12 «, 16, and PI. IV. 

 fig. 16 a, h), and in many instances provided with a broad, thin, 

 smooth, outstanding lip above the ciliated border, and hiding it 

 (PL III. figs. 13 a, 14 «, 15 «, h, and PL IV. figs. 17 a, h, 18 a, 6). 

 This flange-like lip varies in breadth with difi'erent individuals, and 

 in its distance from the ciliated edge (see PL III. fig. 15 6, and 

 PL IV. figs. 17, 18). The surface of the valves is crossed by two 

 strong, and more or less curved or even sigmoidal furrows, varying 

 in width and intensity, as seen in PL III. figs. 12 a, 13 «, 14 a, and 

 15 a. There are consequently three unequal, obliquely transverse 

 lobes. The curve of the hindermost furrow encloses the highest 

 and roundest of the lobes. The middle lobe sometimes curves 

 round ventrally to join the hindermost (as in figs, 13a and 15 a); 

 but sometimes it ends ventrally in an isolated hollow process or 

 spine (broken in figs. 12 a and 14 a). Another difference among 

 the specimens is to be seen in the flange and prickles of the ventral 

 margin. These may both be present (as in PL III. figs. 13 a, 14 a, 

 15 a, 6, and PL IV. figs. 17 and 18). In PL III. figs. 12 a and 16, 

 and PL IV. fig. 16, the fringe only appears. This feature gave 

 origin to Dr. Emmons's name for the species. The swollen lobe 

 not being in front, but behind, vitiates the name given afterwards 

 by Dr. Hall. 



The surface of the valves is always granulose, the granules having 

 difi'erent degrees of coarseness, according to age apparently (see figs. 

 12, 13, 14; in figs. 14 a and 15 a this feature was inadvertently 

 neglected owing to the granules becoming lower, broader, and 

 coalescent). 



The figure given by Prof. Hall resembles PL III. fig. 15 a, except 

 that the outstanding flange is not defined. Prof. Emmons's figure 

 (except that it is a right instead of a left valve) is comparable with 

 PL III. fig. 12 a, but without the ventral process. The interior of 

 a left valve (PL III. fig. 16) shows the reverse aspect. 



This well-marked species occurs in two pieces of stone (marked 

 59725) in the British Museum : — 1. A thin, light brown (weathered) 

 limestone, consisting of small organisms, such as Encrinital joints, 

 Brachiopods, and Polyzoans, with B. ciliata and Primitia minuta 

 (red in colour), standing out more freely on one face than the other. 

 2. A dark grey, thin, similar limestone, with light gre}' shaly 

 ^faces. Both irom Cincinnati, Ohio. 



Also in specimen I. 512, Brit. Museum; a grey limestone seam, 

 weathering brownish grey, made up of small organisms (Encrinital 

 joints, Brachiopods, Polyzoans, &c., with Ostracoda, chiefly B. 

 ciliata). Erom the Hudson-Kiver Group, Cincinnati, Ohio. 



Eigs. 15 and 16, PL III., are in a bluish-grey limestone (weathering 

 brownish) consisting of small organisms, such as Polyzoa, Encrinital 

 joints, fragments of Trilobites, &c., with B. ciliata. Cincinnati 

 Group, Lower Silurian, Cincinnati, Ohio. Given to me some years 

 ago by Dr. E. W. Claypole, F.G.S. 



The edge views in PL IV., figs. 16-18, correspond to the valves 

 in PL III. figs. 12-14 respectively. 



