* 
INTRODUCTION. 7 
from recent forms. It is a rather singular fact, considering the present wide distribution 
of the genus Lepas or Anatifa, and the frequency of the individuals, that not a single 
valve known certainly’ to belong to this genus, or to any of the closely-allied genera, 
has hitherto been found fossil. 
The oldest known cirripede is, as we have seen, a Pollicipes from the Lower Oolite, and 
it does not differ conspicuously from some of the recent species of the same genus; so, 
again, the cretaceous Scalpellum fossula, and the eocene S. guadratum are certainly very 
nearly related to the recent S. rutilum (nov. spec.). Loricula alone is a genus perfectly 
distinct from all living Cirripedia ; and I may here add that of the Tertiary Sessile Cirripedes, 
I have hitherto not seen a single new generic form. This persistence of the same genera 
is somewhat remarkable, considering that amongst ordinary Crustacea nearly all the 
Secondary species belong to extinct genera;” it should, however, be borne in mind that 
Limulus has survived from the Paleozoic period to the present day. The Oolitic, 
Cretaceous, Tertiary, and recent species of Lepadide are all different from each other. By 
looking at the annexed Table, and putting out of question the species of which the age 
is uncertain, we have five common to two stages of the chalk; that is assuming for the 
present that the classification of the stages of the chalk commonly used and here followed, 
is correct. Pollicipes glaber is common to three, and, I believe, to four stages. Scalpellum 
arcuatum occurs in the Chalk-marl, and upper Greensand, and therefore this species also 
extends through three stages ; but there is a slight difference between the specimens from 
the upper and lower stages, which some authors might perhaps consider specific. If 
fossil cirripedia had, like most recent species, very wide horizontal or geographical ranges, 
then, in accordance with a law now generally admitted, a considerable vertical range in 
some of the species is not improbable. 
I may here observe that I am assured by Professors Forchammer and Steenstrup, that 
the formations of Scania and Westphalia are equivalent to that of Faxoe ; and hence to that 
of Maéstricht. I have called these formations the ‘“‘ Maestricht formation,” to distinguish 
them from the common upper or white Chalk. 
1 In a mere catalogue, published without descriptions, in the ‘Jahrbuch’ for 1831, p. 155, by 
Hoenninghaus, Anatifa cancellata is given as a tertiary species: Mr. G. B. Sowerby has stated, in his 
‘Genera of Shells,’ that he has seen a Tertiary specimen of this genus, but he cannot remember which 
valve it was. 
2 Pictet, Traité Elémentaire de Paléontologie, tom. iv, p. 4. 
