270 BULLETIN 93^ UNITED STATES NATIONAL MUSEUM. 



The Platylepadid series is composed of genera having a midrib 

 within each compartment, produced by a median infolding; or when 

 this is not present there is externally a median longitudinal smooth 

 area, or interruption of the sculpture, which may be regarded as the 

 vestige of a former mesial infolding which has left this permanent 

 mark upon the external sculpture after the fold itself has utterly 

 disappeared. So far as known there is no oral " hood." In the selec- 

 tion of hosts the species show catholic tastes. While chiefly (and 

 probably in the beginning) turtle barnacles, they also live on mam- 

 mals (Sirenia), sea-snakes, and fishes, but not one has yet been 

 found on a cetacean. 



The genera of these two series follow, closely related groups being 

 bracketed together. 



Corouulinfp 



Coroiiulid series 



f Xenobalanus. 



1 Tixbicinella. 



rCryptolepas. 

 j [Cetopirus. 



[ Coroniila. 



fPlatylepas. 



Til i 1 Tj • I ICylindrolepas. 



LPlatylepadid series^ "■ •' '■ 



rSteplianolepas. 

 IStomatolepas. 



KEY TO GENERA OF CORONULIN.^. 



o\ Body lengthened, liaving the appearance of a naked peduncuhito oirripede, 

 not contained in the cavity of the wall, which is minute, stai'-shaped, and 

 embedded in the skin of the host. Opercular valves wanting. 



Xenobalanus, p. 2S2. 



a\ Body contained in the cavity formed by the walls; opercular valves present. 



h^. Parietes having similar sculpture throughout, the median part not 



longitudinally sulcate, smoothed, or otherwise differentiated from 



the rest of the parietes; compartments without internal midribs. 



Whale barnacles. 



t'\ Wall of the body-chamber having external radial ribs or folds, 



visible at least on the base; radii well developed, triaugulai". 



(f. Radiating ribs having T-shaped terminal loops which 



unite to form an outer and upper wall Coronula, p. 271. 



(1-. Radiating ribs not forming an outer wall ; sheath trans- 

 versely grooved Criiptolepas, p. 278. 



c*. Tul)ular, annulate, without longitudinal ribs; radii narrow; 



opercular valves well developed TuhicincUa, p. 281. 



h^. Parieties not sculptured evenly throughout, but having a longitudinal 

 sulcus, smooth area, or change in the direction of the sculpture, or 

 having midribs in the compartments within. Turtle, manatee, and 

 snake barnacles, 

 c^. Basal edges of the compartments ribbed or toothed. 



if. Form conic, the orifice decidedly smaller than the basis ; 

 each compartment having a midrib within, serving 

 to support the basis ; inner and basal edges acutely 

 ribbed Plaiylepas, p. 284. 



