220 Transactions. — Geology. 



also unworn specimens have fine spiral lines on the embryonic 

 whorls. Captain Hutton informs me the typical examples 

 from Petane have the embryonic whorls smooth, byt are 

 slightly rubbed, and the spiral sculpture probably erased. 



Odostomia (Pyramis) obsoleta, n. sp. Plate XX., fig. 4. 



Shell minute, ovato-elongated ; whorls 5, slightly convex, 

 the two apical smooth, the first polished, the third whorl with 

 four and the fourth with five delicate spiral grooves, leaving 

 a narrow smooth space at the anterior end of each whorl ; 

 body-whorl nearly twice the length of spire, with eight spiral 

 grooves, six in front of the aperture, anteriorly without 

 sculpture, finely longitudinally striate with growth - lines ; 

 sutures lightly impressed ; aperture ovate, slightly oblique, 

 columella gently curved, the plait indistinct, situate some- 

 what within the aperture ; a narrow deeply impressed area 

 in the umbilical region. Length, 2-5 mm. ; breadth, 1-21 mm. 



Type, Wanganui Museum. 



Locality .—Jih\e-Gla,y cliffs, west of the Wanganui Heads. 



Of this minute species there is but a single example ; it is 

 nearly allied to 0. fasciata, Hutton, but differs in the arrange- 

 ment of the spiral sculpture. 



Lacuna (?) exilis, n. sp. Plate XX., fig. 3. 



Shell minute, subovate, fragile, narrowly umbilicate ; 

 whorls 5, smooth, somewhat polished, the spire-whorls 

 rounded, the penultimate more than equals the first three 

 in length, the body-whorl large, inflated, equals four-fifths of 

 total length of shell, the whorls lightly transversely striated 

 with growth-lines ; sutures impressed ; aperture broadly 

 ovate, slightly oblique, outer lip thin, columella gently 

 curved, the inner lip projecting outwards as a narrow rim, 

 leaving, as it were, a deeply channelled suture extending from 

 the umbilicus to the posterior end of aperture ; the umbili- 

 cus small and deep, with a broad shallow groove proceeding 

 from it to the anterior end of columella. Length, 2-5 mm. ; 

 breadth, 1-6 mm. 



Type, Wanganui Museum. 



Locality. — Blue-clay cliffs, west of Wanganui Heads. 



It is with much hesitation I refer this minute shell to 

 Lacuna, a genus known only from the Northern Pacific and 

 Atlantic. Apart from the projecting rim-like inner lip, it is 

 not unlike this genus, and may be included provisionally. 

 There is but a single example, and further material may assist 

 to determine the true position.''' 



* Since the above was written and read the species has been sub- 

 mitted to Mr. H. Suter, of Christchurch, who, with Professor Boehm, 

 of Freiburg, regards it as a form of Lacuna. 



