Maryland Geological Survey 409 



Haminea cylindrica n. sp. 

 Plate XVIII, Figs. 8, 9 



Description. — Shell cylindrical in outline, slender, usually more or less 

 compressed ; spire involute, body whorl slender, cylindrical ; aperture very 

 narrow posteriorly, outer lip strongly patulous, the inner smooth and 

 gently arcuate ; external surface sculptured with twenty-five to thirty low, 

 broad, flattened, medially sulcated spirals separated by linear interspaces. 



This species is closely related to II. mortoni (Forbes), but the shell 

 is much more cylindrical in outline and the diameter, both of the entire 

 shell and of the body whorl only, is much more uniform in the new species 

 than in H. mortoni. The figured material is squeezed, thus giving the 

 outline a medial pseudo-inflation. 



Occurrence. — Monmouth Formation. Brightseat, Brooks estate near 

 Seat Pleasant, Prince George's County. 



Collection. — Maryland Geological Survey. 



Family ACTEOCINIDAE 



Genus ACTEOCINA Gray 

 [Proc. Zool. Soc, London, 1847, p. 160] 



Type. — Act eon wetherilli Lea. 



The name Actcocina was first used by Gray in 1847, as a possible sub- 

 genus of Acteon. He gave no description but he chose as his type of the 

 new group of forms, " Acteon wetherilli Lea," which is not an Acteon but 

 a representative of the genus Tornatina of A. Adams. Since Gray's publi- 

 cation has the priority, the rules of nomenclature have demanded that the 

 familiar name of Tornatina be replaced by that of Acteocina. 



Shell cylindrical or fusiform, thin, inflated; nucleus papillate and 

 heterostrophous ; spire slightly elevated; suture profoundly channelled; 

 aperture narrow, linear; outer lip simple; columella calloused, bearing a 

 single fold. 



The recent species of this genus are for the most part characteristic of 

 the deeper waters of the warm seas. 



Etymology: Diminutive of Acteon. 



