300 BURTOA. 



Una and Limicolaria. This apparently variable color-pattern 

 is deep-rooted in the organization of the Achatinince. 



Burtoa has no direct relationship with Metachatina, and 

 is evidently nearer to Achatina than to Limicolaria. Its re- 

 semblance to Limicolaria in the entire columella is due to 

 convergence, the younger stages of the two groups being 

 more unlike in this respect than the adults. 



1. B. NILOTICA (Pfeiffer). PL 27, fig. 5. 



Shell subperforate, inflated-ovate, solid, brownish, irreg- 

 ularly streaked with dark chestnut ; spire short, conic, the 

 apex rather acute. Whorls 6, convex, the upper smooth, fol- 

 lowing minutely decussate, the last nearly two-thirds the 

 total length, inflated, subplicate, and latticed with rather 

 widely-spaced spiral lines. Aperture slightly oblique, oval, 

 pearly within; peristome roseate, the margins joined by a 

 thick callous, right margin somewhat thickened, striate, some- 

 what spreading above, columellar margin thick, substriate, 

 forming below an indistinct angle with the basal lip. Length 

 118, diam. 61 mm., apert. 67 mm. long (P/r.). 



Northeast Africa: Sources of the White Nile (Petherick). 



Bulimus niloticus PFR., P. Z. S., 1861, p. 24; Malak. BL, 

 1861, p. 14; Monogr. Hel. Viv., vi, p. 86. Achatina (Limi- 

 colaria) nilotica MART., Mai. BL, xii, 1865, p. 196 ; xiii, 1866, 

 p. 94. L. nilotica PFR., Novit. Conch., iv, p. 5, pi. 110, f . 2. 

 MARTS., Beschalte Weichthiere Ost-Afrikas, p. 94. Livin- 

 hacia nilotica CROSSE, J. de C., 1889, p. 109. SMITH, P. Z. 

 S., 1893, p. 634 (Angoni Land, southwest of Lake Nyasa). 



This species has much superficial resemblance to Stropko- 

 cheilus ovatus and its allies. The typical nilotica is the most 

 northern member of a group numerous in local races, and is 

 distinguished by the comparatively elongate shape and small 

 mouth. 



Var. SCHWEINFURTHI Martens. PL 27, fig. 6. 



Shell thin, the aperture comparatively large, nearly two- 

 thirds the length of the shell ; outer lip thin, only moderately 

 arcuate; columellar margin nearly vertical. 



