fcAMUS, PORTO RICO, ETC. 117 



la. Var. SHUTTLEWORTHI (Martens). PL 24, fig. 74. 



k Larger and comparatively wider than the type, with much 

 weaker riblets and almost no basal keel. Length 17, diam. 

 51/3 mm." (Martens.) 



Porto Rico (Albers coll.) ; Penuelas (Sintensis). 



M. sliuttleworthi MARTENS, Jahrb. d. Malak. Ges., iv, 1877, 

 p. 352 ; Nachrbl., xxiii, 1891, p. 132. 



These large forms intergrade with the small Porto Eican 

 shells, so that no rigid distinction can be made. The keel is 

 completely wanting in some shells, noticeable in others. The 

 specimen figured measures : length 19.5, diam. above aperture 

 5.5, length and width of aperture 5 mm., whorls 12%, but 

 many smaller shells have the keel very weak, almost wanting, 

 such as the original of fig. 73, which measures hardly 13 mm. 

 long. Possibly all Porto Rican microdon are referable to var. 

 thuttleworthi, even when moderately keeled (like fig. 72), 

 and costulate. 



2. M. JOHANNIS Pfeiffer. PL 24, figs. 79, 80, 81. 



" Shell subperf orate, subfusiform-turrite, thin, obliquely 

 plicatulate; brown-corneous. Spire regularly tapering, the 

 apex slightly obtuse, suture moderate, somewhat toothed by 

 the projecting folds. Whorls 11-12, moderately convex, slowly 

 increasing, the last slightly exceeding one-fourth the length, 

 obtusely angular below the middle. Aperture oblique, irreg- 

 ularly rounded; peristome thin, the margins distant, right 

 margin regularly arcuate, expanded, columellar margin 

 dilated, triangularly spreading, having a tooth-like promi- 

 nence within. Length 15, diam. 4 mm." (Pfr.). 



Porto Rico: Aguadilla, in the western part (Gundlach). 



M. johannis PFR., Malak. BL, xxii, 1874, p. 119; Monogr., 

 viii, p. 621 ; Novit. Conch., v, p. 27, pi. 142, f . 7-10. 



This species, which I have not seen, seems to stand close to 

 the Porto Rican race of M . microdon, from which the descrip- 

 tion seems hardly to distinguish it. It is named for the dis- 

 tinguished Cuban naturalist, Dr. Johann Gundlach. A 

 slightly smaller variety, variegated with opaque white, is men- 

 tioned and figured by Pfeiffer (fig. 81). 



