MR. T. H. WITHERS ON 



Structure and Affinities. It is evident from tlie structure of 

 the inner surface of the compartments of this Cir-ripecle, and 

 from the modification of tlie side wall of the compartments to 

 form al?e, that the elements combined to form a shell something- 

 like the compartments in the genus Balcmus. This is proved by 

 the fact that the lines on the inner lateral portions of the rosti-um 

 correspond to, and are obviously made by, the growth-lines of 

 the ala of each latei'al compartment, which was overlapped by the- 

 lateral portions of the rostrum ; similarly shaped lines on the 

 lateral compartment correspond to those on the ala of each 

 carino-lateral compartment which was overlapped by the latei'al 

 compartment ; the more angularly bent lines on the carino- 

 lateral compartments correspond to those on the alae of the 

 carinal compartment which were overlapped by the carino-lateral 

 compartment. In addition, more or less prominent longitudinal 

 ridges are developed in the ujoper portions of the rostral, lateral, 

 and carino-lateral compartments against which the angle of the 

 ala of the adjacent valves abutted. The transverse lines on 

 the portions of the compartments not covered by the alse are 

 similar to those in Balanus, in which they are caused by the 

 successive exuviation of the opercular membi-ane. To a similar 

 cause may be attributed those in the present Oirripede. 



That tliis form is a sessile Oirripede is, I think, beyond doubt, 

 and the irregularity in shape of the several compartments, as 

 well as the fact that some are externally and irregularly ridged 

 longitudinally and others distorted with linear depressions, is- 

 further evidence in support of this conclusion, for these features 

 could be caused only by the irregularity in the surface of 

 attachment. In accordance with the above interpretation, six 

 compartments would complete the wall of the shell, as in 

 Balcmus ; and it is important to note that every fra,gment in 

 the present collection can be allocated to one of the six valves 

 figured. (PL LXXXV. & Text-figs. 139, 140.) 



The shell of this form could not have been very strong, for, in 

 comparison with the great length attained by the compartments, 

 the walls are" relatively quite thin. The compartments could 

 have been only weakly attached, and are in consequence always 

 found quite apart fi'om one another. Moreover, the absence of 

 radii, together with the absence of sutural edges to the alte and 

 the comparatively feeble ridges or shoulders developed on the 

 inner surface, and against which only the angles of the alas could 

 have abvitted, show quite clearly the great structural frailty of 

 the shell. It could hardly have been a littoral barnacle. 



Although this form agrees with the typical species of the genus 

 Baldnus in the number of compartments forming the walls of the 

 shell, it differs markedly in the structure of these compartments. 

 These differences are (1) the absence of radii, (2) the simpler 

 structure of the alfe, (3) the absence of longitudinal ribs on the 

 inner surface, (4) the feebly developed sheath, as well as tlie 



