24 ORDER II. PEDUNCULATE. 



at the base to some marine body, from which the animal cannot displace 

 it. We include them in the following six genera : 



llthotrya. pollicipes. 



Pentelasmis. Cinaras. 



SCALPELLUM. OtION. 



LlTHOTRYA, Sowerby. 



Testa octovalvis, irregulariter subpyramidalis, lateribus compressis, val- 

 vis sex contiguis, insequalibus, lateralibus, inferioribus minimis 

 valva unica dorsali magna, ligulata ; unica antica minutissima 

 appendice testacea, patellam inversam referens, ad basem pedun- 

 culi. Animal saxorum cavos ab ipso terebratos incolens. 



This remarkable Lepas was first described by Sowerby, who considers 

 the animal to be intermediate in its organization between that of the 

 Sessiles and Pedunculati. It is somewhat of an irregular, compressed, 

 pyramidal form, having the top of the peduncle surrounded by rows of 

 very small scales. The shell consists of eight unequal pieces ; six are 

 contiguous and lateral, one dorsal, and one anterior, but very small. 

 The peculiar and distinguishing character, however, of Lithotrya is in 

 the appearance of an irregular, testaceous, cup-shaped appendage, resem- 

 bling the inverted shell of a Patella, to the inside of which the base of 

 the peduncle is attached. This patelliform cup may be considered as ana- 

 logous to the testaceous base which characterizes the shell of Balanus, 

 and is always fixed to the bottom of a deep irregular cavity in limestone 

 rock, evidently perforated by the animal. 



Example. 



PI. XI. Fig. 1 to 3. 



Lithotrya dorsalis, Sowerby, Genera of Shells, No. 8. Enc. Meth., 



pi. 166. f. 5. 

 Lepas dorsalis, Solander. 

 Litholepas dorsalis, De Blainville. 



