. Bulletin of the British Museum (Natural History), Geology. MIDDLE JURASSIC OSTRACODA loi Description. Carapace oval-subrectangular in outline with well rounded anterior and posterior margins, slightly concave mid-dorsal margin and antero-medially incurved ventral margin. The carapace is constricted slightly in the mid-dorsal region, and is noticeably swollen in the postero-dorsal region. Greatest length of carpace through mid-point, greatest height in the anterior third, greatest width in the posterior third. Shell surface ornamented by prominent 5-6 sided pits. Ventrally the reticulate orna
. Bulletin of the British Museum (Natural History), Geology. MIDDLE JURASSIC OSTRACODA loi Description. Carapace oval-subrectangular in outline with well rounded anterior and posterior margins, slightly concave mid-dorsal margin and antero-medially incurved ventral margin. The carapace is constricted slightly in the mid-dorsal region, and is noticeably swollen in the postero-dorsal region. Greatest length of carpace through mid-point, greatest height in the anterior third, greatest width in the posterior third. Shell surface ornamented by prominent 5-6 sided pits. Ventrally the reticulate ornament is somewhat subdued and is dominated by a series of longi- tudinal ridges. A low, smooth, eye swelling is situated at the anterior cardinal angle. Left valve larger than the right which it over-laps along the ventral margin and slightly. V. • V^^^;:.iO:':->V-^v.';.::-;.-.^ Fig. 7. Muscle scars, Caytonidea faveolata sp. nov. Paratype, , approx. X 250. in the region of the anterior cardinal angle. Hinge antimerodont, seen only in the right valve : 4 anterior and 5 posterior teeth observed ; median groove long and locellate. Duplicature of moderate width, the inner margin and line of concrescence coinciding. Radial pore canals long, straight and widelyspaced, yobservedanteriorly. Muscle scars with rounded antero-dorsal antennal scar (Type A). Dimensions Holotype , carapace (PL 2, figs. 1-4), length 0-56 mm. ; height 0-33 mm. ; width 0-30 mm. , carapace (PL i, figs. 13, 14 ; PL 2, figs. 5, 6), length 0-65 mm. ; height 0-37 mm. ; width 0-33 mm. , carapace length 0-56 mm. ; height 0-34 mm. ; width 0-27 mm. Remarks. Externally similar to Southcavea reticulata Bate (1964 : 27, pi. 10, figs. 3-14 ; pi. II, figs. 1-4), Caytonidea faveolata differs in the presence of an eye swelling, type A muscle scar arrangement as against type D, and in being less convex in dorsal view. The reticulate ornament of S. reticulata differs markedly from that of C. f
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