22 ORDER I. SESSILES. 



PI. VIII. Fig. 2. 



Clitea verruca, Sowerby, Genera of Shells, No. 33. 

 Lepas verruca, Gmelin. 

 Creusia verruca, Lamarck. 

 Verruca Stromii, Gray. 



CREUSIA, Leach. 



Testa convexo-conica, orbiculata, valvis quatuor inaequalibus lateraliter 

 ferruminatis composita ; apice pervio, basi testacea, modo calici- 

 formi, modo tubulari, madreporis infixa, clausa. Operculum inter- 

 num, bipartitum, valvis quatuor compositum. 



The genus Creusia was also instituted by Dr. Leach, and, like the fol- 

 lowing, is always found deeply imbedded in the surface of different kinds 

 of Corals and Madrepores, this being its peculiar mode of habitation. 

 The shell is of a conical patelliform shape, consisting of four pieces 

 closed upon a grooved testaceous base, penetrating the Coral in the 

 shape of a cup or tube. The operculum is bipartite, composed of four 

 valves. 



Example. 



PI. IX. Fig. 1 to 6. 



Creusia gregaria, Sowerby, Genera of Shells, No. 18. 



PYRGOMA, Savigny. 



Testa corapresso-conica, indivisa, superne convexa; apice pervio, basi 

 testacea, modo caliciformi, modo tubulari, madreporis infixa, clausa ; 

 apertura. parva, subovali. Operculum internum, bipartitum, valvis 

 quatuor compositum. 



The genus Pyrgoma was proposed by Savigny, but divided into four 



