484 Systematic Paleontology 



A fragment was collected from the Monmouth which suggests Welter's 

 species. The external surface of the Maryland form, however, is sculp- 

 tured with probably about half a dozen longitudinal ridges. The species 

 has more of the general aspect of Vermetus than of an annelid, and 

 although no evidence of internal septse is attainable there is some reason 

 to believe that the shell was made up of three component layers instead of 

 two as in the tubiculous annelids. Other tubes apparently new but too 

 imperfect to describe occur in the Matawan of Anne Arundel County. 

 They are smaller and straighter than the tubes from the Monmouth and 

 often more or less compressed laterally. 



Occurrence. — Monmouth Fokmation. Brightseat, Prince George's 

 County. 



Collection. — Maryland Geological Survey. 



Genus LAXISPIRA Gabb 

 [Proc. Acad. Nat. Sci., Fhila., 1876, p. 301] 



Type. — Laxispira lumbricalis Gabb. 



" Shell spiral, dextral, whorls with a circular cross-section, few in num- 

 ber, and so rapidly descending as to form an open spiral ; aperture simple, 

 lips thin. 



" A curious genus, the relations of which are not clear to me. I propose 

 it to receive some shells which have been long known as internal casts in 

 the marls of New Jersey, but of which the surface was unknown until 

 quite recently. In general form they might be compared to a partially 

 uncoiled Turritella. From that genus they differ, however, in the whorls 

 not being in contact, and from Vermetus and the allied genera in being 

 regular spirals, but not having the apex either turritelloid or attached." 

 —Gabb, 1876. 



Dall * considers the genus as a synonym of Siliquaria, but the coiling is 

 conspicuously regular, more so than in any known species of Siliquaria. 

 For that reason it seems desirable to keep the two groups distinct until 

 evidence is produced which demands their union. 



Etymology: Laxus, loose; spira, spire. 



1 Trans. Wagner Free Inst. Science, Phila., 1892, vol. iii, pt. ii, p. 307. 



