178 Mr. T. H. Witliers on some 



With regard to the so-called subcarinse and subrostra 

 figured by Bosquet (1857), it is highly probable that they 

 also are small examples of carinse and rostra, and the seven 

 supposed lower lateral plates, of which two show exteriorly 

 a median basal notch, may be referred Avith more justification 

 to Bosquet's species Brachylepas lithotryoides. 



There is also much uncertainty with regard to the valves 

 considered by other authors to belong to the lower whorl of 

 P. fallax, and, in fact, there is no real evidence that P.fallax 

 had a lower whorl of valves, for in the absence of any lower 

 lateral plates one cannot quite see how this species could 

 have had subrostra and subcarina. 



Therefore, in default of more precise evidence to the con- 

 trary, 1 prefer to include Pollicipes fallax in the new genus 

 Pycnolepas, with which it more closely agrees. 



According to Mr. Brydone, P. fallax is by far the com- 

 monest of the Cirripedes in the Trimingham Chalk. It is 

 met with occasionally in the mucronata-zone of Norvvich, 

 and Dr. H. P. Blackmore has collected in the neighbourhood 

 of Salisbury a single carina and rostrum from the mucronata- 

 zone and a single rostrum from the guadratus-zone. The 

 most interesting specimen, one which constitutes the earliest 

 record for this species, is a beautifully preserved rostrum 

 (PI. VIII. fig. 5) obtained by Dr. Blackmore from the base 

 of the upper third of the M. coranguinum-zone at Quid- 

 hampton, near Salisbury. Although this valve has a median 

 ridge and is so much incurved that I think it must be a 

 rostrum, it certainly is comparatively narrow for such a valve. 

 It has a ratlier difi'erent appearance, owing to its being more 

 strongly and irregularly ridged than the valves from higher 

 horizons. 



Measurements. The valves figured in this paper (PI. VII. 

 figs. 10-14) measure respectively : — 



Length. Breadth, 



mm. mm. 



Rostrum 141 9-2 



Scutum 180 9-2 



Upper latus 12'5 2-8 



Tergum 16-8 108 



Carina 17'4 6-5 



? Rostrum (PI. VIII. fig. 5) 77 37 



Only two valves are known to me from the English Chalk 

 that exceed the above in ><ize, and these are a tergum from 

 the Trimingham Chalk, said by Dr. Woodward (1906, p. 345) 

 to be 19 mm. long and 11 '5 mm. broad, and a carina in the 



