354 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



0. I. subplanulata both on the upper and lower surfaces, which sug- 

 gests Obba mesai, but it differs from 0. I. subplanulata in having the 

 whorls more inflated, in having a broader umbilicus, and in having 

 malleations on both the upper and lower surfaces. 



OBBA LISTERI SUBPLANULATA (Mollendorff) 



Plate 90, Figure 2 



1898. Obbinalisteri subplanulata Mollendorff, Abh. Naturf. Ges. Gorlitz, vol. 22, 

 p. 86. 



1905. Obbina listeri subplanulata Mollendorff, Kobelt, and Winter, Semper's 

 Reisen im Archipel der Philippinen, vol. 10, pt. 1, p. 23, pi. 6, fig. 7. 



The shell is small, not acutely keeled at the periphery, but rather 

 strongly angulated. The nuclear whorls are pale brown; the post- 

 nuclear whorls are of pale buff color with a series of rather large, 

 irregular, chestnut-brown spots midway between the summit and 

 the periphery of the turns, and a less conspicuous band halfway 

 between this and the summit. There are other lesser blotches also 

 present on the upper surface. The base is pale yellow, marked with 

 a broad interrupted band of brown spots about one-third of the dis- 

 tance between the periphery and the umbilicus anterior to the pe- 

 riphen r . The peristome is white, while the interior of the outer lip is 

 pale brown with the external bands showing darker through the sub- 

 stance of the shell. The nuclear whorls are marked by fine incre- 

 mental lines and microscopic spiral striations. In the postnuclear 

 whorls the incremental lines and spiral striations become stronger 

 except on the last whorl, where the latter element somewhat weakens 

 and where the conspicuous crisscross sculpture presents itself. The 

 incremental lines extend on the lower surface, which is also marked 

 by fine spiral striations and crisscross sculpture. The aperture is 

 rather broadly ovate with the peristome expanded and reflected to 

 cover one-third of the umbilicus. There is a conspicuous broad fold 

 on the inside of the inner lip. 



The specimen described and figured, U.S.N.M. No. 382933, comes 

 from the Quadras collection and was collected on Ambil Island, the 

 type locality for this subspecies. It has 4.7 whorls, and measures: 

 Height, 11.5 mm; greater diameter, 28.1 mm; lesser diameter, 23.1 mm. 



This subspecies strongly suggests the Obba mesai group in the con- 

 spicuous spotting of the interrupted spiral bands of the base. It 

 differs from the members of this group by the much more strongly 

 angulated periphery. In this respect it is much more closely allied to 

 Obba listeri. It is nearest related to 0. I. caloocana from Caloocan, 

 from which it can at once be distinguished by the absence of the mallea- 

 tions on the base. 



