WEST AMERICAN PYEAMTDELLID MOLLUSKS. 21 



Subgenus LONGCHiEUS Morch. 



Longchv us UoRCH, Malak. Blatt., vol. 22, 1875, p. J5S. 



Shell elongate-conic, not umbilicated, having three columellar 

 folds, a basal fasciole and peripheral sulcus. The entire surface is 

 marked by fine lines of growth and microscopic spiral striations. 



Type. — PyramideUa punctata Schubert and Wagner. 



KEY TO THE SPECIES OF THE SUBGENUS LONGCH^US. 



Shell variegated udamsi, p. 21. 



Shell not variegated. 



Shell rose-pur])le anteriorly- bicnlnr, j). 22. 



Shell brown. 



Adult shell more than 18 mm. long mexicana, p. 23. 



Adult shell less than 14 mm. long. 



Sutures very strongly channeled conicu, p. 23. 



Sutures moderately channeled mazatlanica, p. 24. 



PYRAMIDELLA (LONGCH^US) ADAMSI Carpenter. 



Plate 1, figs. 6, 6a. 



PyramideUa adarnsi Carpenter, Rept. Moll. West Coast Amer. Brit. Ass. Adv. 

 Sci. (for 1863), 1864, pp. 546, 547. = Obeliscus conicus jun. Carpenter, Cat. 

 Mazatlan Shells, 1856, pp. 409-10. = Obeliscus variegatus Carpenter, Ann. 

 Mag. Nat. Hist., 3d ser., vol. 14, 1864, p. 46. 



The type of this species is a very young individual of five post- 

 nuclear whorls which was taken from a species of Chama at Mazatlan, 

 Mexico. It is on tablet 1951 of the Liverpool collection in the 

 British Museum. 



Shell elongate-conic, early whorls white, later ones diversely 

 variegated, frequently dark brown on the later turns. It is this 

 striking variegated color pattern which at once flistinguishes this 

 species from the other w^est American forms. The spaces between 

 the sutures are crossed by light areas, which are vertical in the 

 middle, bending suddenly forward at the periphery and the summit, 

 thus forming ") -shaped areas. The space immediately below the 

 peri])heral sulcus on the base has short light areas, corresponding to 

 those above the sulcus, but with retractive slant. The space between 

 these light areas, near the summit, forms a series of elongated dark 

 spots. The varices which are dis])osed at irregidar intervals are 

 chestnut brown, preceded usually by a })and of white. Posterior 

 half of the base light chestnut brown; anterior white. Nuclear 

 whorls small, two, forming a ])lanorboid spire whose axis is at right 

 angles to that of the succeeding turns, in the first of which it is about 

 one-half immersed. Post-nuclear whorls flattened; moderately 

 shouldered at the summit, which is crenulated. Perij)hery with a 

 2565— Bull. 68—09 3 



