FOSSIL CIRRIPEDIA. 



Fig. 8a, Coronula barbara, rostrum, external view ; nat. size. 



8(5, ,, ,, „ viewed internally; twice nat. size. 



8c, „ ,, lateral compartment, internal view. 



Sd, „ „ internal view, much enlarged, of small portion of basal margin 



of folded wall. 

 Be, ,, „ external view, greatly enlarged, of small portion of surface of 



folded walls, near the basal margin ; (r r) the transverse 

 ridges of growth. 

 The following letters of reference apply to all the figures of Coronula : 



a, sheath marked transversely in the upper part by the attachment of the 



opercular membrane. 

 a', ala 



b, furrow on each side of (a), receiving the edge of the thick ala of the 



adjoining lateral compartment. 



c, special plate, on which the ala rests. 



d, radius, on the edge it may be just seen to consist of an outer layer (the 



normal radius), and a much thicker inner part (the pseudo or com- 

 plementary radius) formed of oblique denticulated septa. 



e e' e", basal edge of wall, which from its commencement at e, or e", can be 

 followed, folding up to near the basal edge of the sheath, to its 

 termination at e" or e. 



//, serrated lines of junction between the folds of the wall. 



Fig. da, Verruca Stromia, much enlarged, engraved from a recent specimen, only certain 



valves having been found fossil. 

 9<5, ,, „ fixed scutum and tergum, internal views. The following 



letters apply to both these figures : 



a, rostrum. 



b, carina. 



s, moveable scutum, s', scutum fixed and modified so as to form part of shell. 



t, moveable tergum, t', tergum fixed, forming part of shell. 



In s, and s', a is the occludent margin ; b, the basal margin ; m, the plate 

 to which the adductor muscle is fixed. 



In s and s', the tergal margin is marked by small dashes ; (') being the 

 upper articular ridge, and (") the second or lower articular ridge : in 

 s' (") is called the parietal portion of the valve. 



In t and t', the scutal margin is marked by small dashes ; (') being the first 

 and upper articular ridge, hardly distinct from the occludent margin* 

 and called in t' the occludent rim ; (") is the second or middle, and 

 ("') the lower or third articular ridge, called in t' the parietal portion of 

 the valve : x is the carinal margin, called in t' the carinal rim, and z 

 the basal margin. 



Fig. lOflt, Verruca prisca, five times nat. size. 



105, 10c, ,, scutum and tergum, external views; engraved from a Belgian 



Cretacean specimen, the opercular valves not having been 

 found in England. 



