86 U.S. NATIONAL MUSEUM BULLETIN 29 5 



Dimensions.— Adult female USNM 121363, left valve, length 0.74 

 mm, height 0.43 mm; right valve, length 0.73 mm, height 0.38 mm. 



Habitat. — In the Bahamas and Bermuda collections, B. (G.) 

 coronata is characteristic of the coral reef front rather than the quieter 

 lagoonal or back-reef environments. This close association ^^'ith the 

 coral masses themselves rather than subsidiary biotic microhabitats 

 duplicates the knoA\Ti distribution of Triebelina sertata on reefs at 

 Nosy Be, Madagascar. Thus the similarity of carapace exteriors of 

 Triebelina and Glyptobairdia represents convergence due to similar 

 habitat rather than phyletic aflSnity. 



Affinities. — No other ornamented species of Bairdoppilata are 

 known. The Triassic genus Medwenitschia KoUmaim bears a geo- 

 metrically similar pattern of ridges. 



Remarks. — Rome (1960) has described the appendages of this 

 species in some detail; only the most significant characters are reillus- 

 trated here. 



BYTHOCYPRIDINAE, new subfamily 



Type-genus. — Bythocypris Brady, 1880, p. 45. 



Diagnosis. — Carapace usually thin, smooth, cyprid in aspect; hinge 

 weak; adductor scars arranged in an anterior row of three horizontal 

 scars plus one posteroventral scar, all scars may be divided but not 

 separated; frontal, mandibular, and dorsal scars usually conspicuous. 



Antennules wdth robustly proportioned podomeres, setae no longer 

 than podomere sequence; antennae stout ^\'ith podomere 6 having a 

 simple stout distal claw and several smaller simple setae, none fused; 

 maxilla \\dth 6-10 unfeathered setae on posteroventral platelet; first 

 thoracic leg of male sometimes shghtly reflexed; vibratory plate of 

 first thoracic leg oval, \\'ith 4-15 unfeathered setae and few feathered 

 setae; furca \rith 3-7 setae; genital lobe of female with oval chamber 

 and uncoiled tube; brush-shaped organ of male mth sides equally long. 



Affinities. — Some species in this subfamily have podomere propor- 

 tions that recall those of juveniles in the Bairdiinae. In podomere 

 fusion and proportions, setae counts and structure, vibrator}^ plates, 

 and many other characters this group retains flexibiUty of morpho- 

 logic expression where the homologous structures of the Bairdiinae 

 have become fixed in a rigid pattern. The tendency toward reflexion 

 possible in some males and the conspicuous dorsal muscle scars are 

 properties characteristic of Cypridacea; othermse aU soft-part affini- 

 ties of this group are bairdiid. Juveniles of some species have a 

 frustrating capacity for developing a calcified inner lameUa and other 

 marginal structures comparable to though not as strongly developed 

 as those of the adult; to my knowledge, such a phenomenon is known 

 elsewhere only in the family Macrocyprididae of the Cypridacea. 



