66 LEPADID.E. 



habitants of deep water; on the other hand, most of 

 Pollicipes,* of Ibla, and Lithotrya are littoral forms. The 

 species of Lithotrya have the power of excavating burrows 

 in calcareous rocks, shells, and corals ; and the singular 

 manner in which this is effected, is described under that 

 genus. Anelasma has its sub-globular peduncle deeply 

 embedded in the flesh of Northern Sharks ; and I have 

 seen instances of the basal end of the peduncle of Con- 

 choderma aurita, being sunk into the skin of Cetacea ; in 

 the same way the point of the peduncle in the male of 

 Ibla, is generally deeply embedded in the sack of the 

 female. I believe in all these cases, the cementing sub- 

 stance affects and injures the corium or true skin of the 

 animal on which the creature is parasitic, whilst the sur- 

 rounding parts, being not injured, continue to grow 

 upwards, thus causing the partial embedment of the 

 Cirripecle. In the case of Anelasma, we have growth at 

 the end of the peduncle, and consequently downward 

 pressure, and this may possibly cause absorption to take 

 place in the skin of the shark at the spot pressed on. 



Geological History. — Having treated this subject at 

 length, in the volume of the Palseontographical Society 

 for 1851, 1 will not here enter on it : I will only remark, 

 that the Lepadidae or Pedunculated Cirripedes are much 

 more ancient, according to our present state of know- 

 ledge, than the Balanidse. The former seem to have 

 been at their culminant point during the Cretaceous 

 Period, when many species of Scalpellum and Polli- 

 cipes, and a singular new genus, Loricula, existed; 

 Pollicipes is the oldest genus, having been found in the 

 Lower Oolite, and, perhaps, even in the Lias. The fossil 

 species do not appear to have differed widely from 

 existing forms. 



* I am informed by Mr. L. Reeve that Pollicipes mitella is eaten on the 

 coast of China; and Ellis states ('Phil. Trans./ 1758) that this is the case 

 with P. cornucopia on the shores of Brittany. It is well known that the 

 gigantic Balamis psitlacus, on the Chilian coast, is sought after as a delicacy; 

 and I am assured, by Mr. Cuming, that it deserves its reputation. 



