66 U.S. NATIONAL MUSEUM BULLETIN 295 



other surface ornament present. Two or three posteroventral marginal 

 spines are somewhat larger than others, marginal denticulation absent. 

 Hinge narrow but deeply incised, all parts smooth. Muscle-scar pattern 

 conspicuous as glassy irregular scars in otherwise translucent yellow- 

 white carapace, arranged in four diagonally offset rows. 



Dimensions.— USNM 121331, left valve, length 0.46 mm, height 

 0.24 mm. 



USNM 121332, right valve, length 0.46 mm, height 0.22 mm. 



Distribution. — In sand among coral patch reefs at Ambariobe, 

 Nosy Be, Madagascar. Possibly misidentified as B. tuberculata by 

 Brady (1880) from the Admiralty Islands and (1890) from Noumea, 

 New Caledonia. 



Affinities. — Bairdia tuberculata Br&dy , 1880 [— Bairdia rhomboidea 

 Brady, 1867 (not Kirkby)] is of similar rhomboidal shape, but its 

 exterior is entirely reticulate, without lateral spines; the species was 

 first reported from Mauritius and has since been reported from Colon- 

 Aspinwall, Panama. Specimens assigned to B. tuberculata from the 

 Admiralty Islands and New Caledonia were described as having tiny 

 tubercles and probably belong to T. schyroconcha. 



Bairdoppilata Coryell, Sample, and Jennings, 1935 

 Bairdoppilata (Bairdoppilata) Coryell, Sample, and Jennings, 1935 



Bairdoppilata Coryell, Sample, and Jennings, 1935, p. 3. 



Type-species. — Bairdoppilata martyni Coryell, Sample, and 

 Jennings, 1935, p. 3, figs. 1, 2. 



Diagnosis. — Carapace with rounded contours, lateral outline with 

 slightly concave anterodorsal and posterodorsal margins; somewhat 

 produced posterior. Hinge with auxiliary dentition at the anterior and 

 posterior ends, 4-6 tiny denticles on ends of right valve ridge articu- 

 lating with sockets beneath left valve overlap. Muscle-scar pattern 

 consists of 8-10 scars in three widely spaced horizontal or arcuate 

 rows. 



Antenna with anterodistal seta enlarged to equal distal claw in 

 size and appearance; fused claw smooth. Four unfeathered setae of 

 vibratory plate of first thoracic leg segregated proximaUy, all of equal 

 length. Furca with 7 setae, all long. 



Description. — Carapace moderately thin, translucent; opaque 

 spots characteristically arranged in a distinctive pattern, consisting of 

 small central suboval spot, anterior and posterior spots, possibly also 

 a posterodorsal spot and one or more other dorsal spots. Surface 

 smooth with abundant very tiny pits. Lateral outline of left valve 

 with broadly arched dorsal margin, broadly and obliquely rounded 

 anterior margin, produced caudate posterior termination, straight 



