INTRODUCTION. 5 



The existence of a Cretaceous Verruca is an apparent exception to the rule, as this genus has 

 hitherto always been ranked among Sessile Cirripedes ; but Verruca, as we now know, must 

 be placed in a family by itself, namely, the Verrucidee, quite distinct from the Balanidse. 

 Balanus is the oldesu genus as yet known ; it first appeared in Europe and North America, 

 during the deposition of the eocene beds ; and was at that time, as far as our information at 

 present serves, represented by very few species. In South America, one species of Balanus 

 abounds in individuals in the ancient Patagonian tertiary formation. I have seen, in the 

 British Museum, specimens said to have come from the eocene nummulitic beds, near the 

 mouth of the Indus, belonging to that section of the genus, which has the walls and 

 basis permeated by pores. Generally, the extinct forms belong to the section, which has 

 the parietes not permeated by pores. During the miocene and pliocene ages, Sessile 

 Cirripedes abounded. No extinct genus in this family has hitherto been discovered. It is 

 singular, that though the Chthamalinse approach much more closely than do the Balaninge 

 to the ancient Lepadidse, of which so many species have been found fossil even in the 

 older Secondary formations, yet that only one species of one genus of this sub-family has 

 been hitherto found in any deposit ; and that species is the still existing Pachylasma 

 giganteum, in the modern beds of Sicily. During the epoch of the Glacial deposits in 

 Scandinavia, Scotland, and Canada, the still existing species seem to have abounded ; 

 and they attained larger average dimensions than the same species now do on the shores 

 of Great Britain, or even on the shores of the northern United States, where the average 

 size seems larger than on this side of the Atlantic. 



I already have given my reasons for very seldom naming any Sessile Cirripede 

 without examining the opercular valves : it has been owing to this, as it appears to me, 

 proper want of caution, that there are so many nominal species. Thus it is made to 

 appear in catalogues, that the tertiary seas abounded with species of Balanus to an 

 extent now quite unparalleled in any quarter of the world. Bronn, 1 for instance, in his 

 invaluable ' Index Palseontologicus,' gives the names of thirty-five Balani, found fossil in 

 Europe, and I have not counted those found only in alluvial deposits, as they would 

 certainly be the same as the still living species. Now I know only eleven recent Balani 

 on the shores of all Europe, from the North Pole to lat. 30°; and of these I doubt whether 

 B. balanoides mdjmprovisus have been found fossil. In the Red Crag there is one extinct 

 Balanus : in the Coralline Crag, which seems to have been very favorable to the existence 

 of Cirripedes, there are six species of Balani, of which two are absolutely extinct, and 

 one does not occur in any neighbouring sea -. in the Eocene formations the species seem 

 to have been rare, and I have seen only one, and that is an extinct form. Taking these 

 several facts into consideration, and bearing in mind that Cirripedes usually range widely, 



1 To save any other person interested in fossil Cirripedia, going through the several works quoted by 

 Bronn, I have given some remarks on his list of species, in an appendix at the end of the Balanidee, in my 

 volume published by the Ray Society. 



