36 FOSSIL CIRRIPEDIA. 



Pyrgoma Anglicum. Tab. II, fig. la — 7c. 



Pyrgoma Anglica. G. B. Sowerby. Genera of Recent and Fossil Shells, fig. 7, 



No. 18, Sept. 1823 (sine descript.). 

 Megatrema (Adna) Anglica. J. E. Gray. Annals of Philosoph. (new series), vol. x, 



Aug. 1825. 

 Pyrgoma sulcatum. Philippi. Enumeratio Molluscorum Sicilise, Tab. 12, fig. 24, 

 (1836). 

 — angltca. Brown. Illustrations of Conchology, (2d edit., 1844), Tab. 53, 



fig. 27— ?9. 



P. testa abrupte conicd, purpureo-rubrd ; orijicio o^ato, angusto ; basi porosd, plerumque 

 e coralio exserta .- scuto et iergo subtriangularibus. 



Shell steeply conical, purplish red .- orifice oval, narrow : basis permeated by pores, 

 generally exserted out of the coral : scutum and tergum sub-triangular. 



Fossil in the Coralline Crag (Ramsholt) Mus. S. Wood. 



Recent on the south coast of England and of Ireland, (12 to 45 fathoms, Forbes and MacAndrew) ; 

 Sicily ; Madeira ; St. Jago, Cape de Verde Islands ; generally attached to the edge of the cup of a 

 Caryophyllia, in deep water, but at St. Jago within the tidal limits. 



I have considered this fossil as identical with the recent species, but, as may be seen 

 from the following description, it presents several slight differences; yet they are such that 

 I dare not found a new species on only a few specimens thus characterised. 



The shell is steeply conical, slightly compressed, with the lower part having rounded, 

 approximate, radiating ribs ; these ribs seem to be more prominent in the fossil than in 

 the recent specimens. Colour dull purplish-red. Orifice oval, small, and narrcw. The 

 basis is not deeply conical, and occasionally is even flat: in the Crag specimens it is almost 

 wholly imbedded in the coral to which it is attached ; but in recent specimens it is gene- 

 rally exserted. Externally the basis is furnished with ribs corresponding with those on the 

 shell. The largest recent specimens which I have seen, from St. Jago, was '22 of an inch 

 in basal diameter ; but some few of the British specimens are nearly as large, and one of 

 the fossils from the Coralline Crag a very little larger. 



The scuta and terga are of the ordinary shape of these valves in Balanus and its 

 allies. Scutum (fig. lb) triangular, with the basal margin a little curved and protuberant ; 

 adductor and articular ridges distinct from each other, moderately prominent; there is 

 a small hollow for the lateral depressor muscle : in the fossils, the adductor ridge (as 

 figured) is more distinct from the articular ridge, and consequently the cavity for the 

 lateral depressor muscle is wider and less deep that in recent specimens. Tergum, I have not 

 seen a fossil specimen, but have figured a recent valve (7c) ; it is triangular, with the spur rather 

 narrow, moderately long, placed near, but not confluent with, the basi-scutal angle of the 



