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, thej also lire 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. 



Coronulid series. . 



Coronulinse 



.Xenobalanus. 

 .Tubicinella. 



fCryptolepas. 



[Cetopirus. 

 .Coronula. 



jTlatylepas. 



.Platylepadid seri J ICylindrolepas. 



fStephanolepaa. 



[Stomatolepas. 



KEY TO GENERA OF CORONULIN.E. 



a 1 . Body lengthened, having the appearance of a naked pedunculate cirripede, 

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

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



Xcnob<il(tnits, p. 282. 



a 2 . Body contained in the cavity formed by the walls; opercular valves present. 



b\ Parietes having similar sculpture throughout, the median part not 



longitudinally silicate, smoothed, or otherwise differentiated from 



the rest of the parietes ; compartments without internal midribs. 



Whale barnacles. 



c 1 . Wall of the body-chamber having external radial ribs or folds, 



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



d 1 . Radiating ribs having T-shaped terminal loops which 



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



r? 2 . Radiating ribs not forming an outer wall ; sheath trans- 

 versely grooved Criiptoh'inis, p. 278. 



c 2 . Tubular, annulate, without longitudinal ribs ; radii narrow ; 



opercular valves well developed TubicincUa, p. 281. 



b*. 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 1 . Basal edges of the compartments ribbed or toothed. 



d l . 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_. Platylepas, p. 284. 



