1883.] 'lightning* AND 'porcupine' EXPEDITIONS. Ill 



in a small but deep perforation and is enclosed by a more or less sharp 

 and distinct ridge. The tentacles of the animal are ciliated as in 

 Trochus and Rissoa, which is not the case in Lacuna. The shell 

 varies in the comparative height of the spire, as well as in the sculp- 

 ture as shown in the variety costulata. That variety is Lacuna 

 margaritifera of Watson. 



\/ 2. CiTHNA cinctaS Jeffreys. (Plate XX. fig. 8.) 



Shell globosely conical, thin, opaque, rather glossy : sculpture, a 

 few and remote spiral striae, of which there are from 3 to 6 on the 

 last whorl and 1 or 2 on the penultimate and other whorls ; the 

 most ])rominent of these striae is one below the suture, which gives 

 the whorls a somewhat carinated appearance ; this stria is minutely 

 tubercled on the upper whorls : colour white : spire turreted, ending 

 in a twisted point : whorls 5, swollen ; the last exceeds two fifths of 

 the whole shell, the others gradually enlarging : suture deep : mouth 

 circular, bluntly angulated at the base : outer lip thin, slightly ex- 

 panding, and folded over the pillar : inner lij> attached to the pillar : 

 umbilicus shallow, enclosed by a semicircular ridge and ending in a 

 small but deep perforation. L. O'l, B. O'l. 



* Porcupine ' Exp. 1870 : Atl. St. 16. Two specimens. 



1/ 3. Cithna carinata ^ Jeffreys. (Plate XX. fig. 9.) 



Shell compactly pyramidal, thin, opaque, glossy : sculjjfure con- 

 sisting of a single keel which surrounds the periphery or middle of 

 each whorl and makes it angular ; under the microscope the surface 

 appears closely granular or fretted ; the base is encircled by a few 

 slight striae : colour white, except as to the uppermost whorls, which 

 are as in C. tenella yellowish-brown : spire turreted, ending in a 

 symmetrical apex : whorls 5-6, angulated, flattened between the 

 suture and the keel, regularly increasing in size : suture very deep : 

 mouth quadrangular, sharply pointed at the base : outer lip thin, 

 reflected behind : inner lip narrow, attached to the pillar : umbilicus 

 saucer-shaped, enclosed by a slight and inconspicuous ridge and 

 terminating in a small perforation. L. 0*1, B. 01. 



' Porcupine ' Exp. 1870 : Atl. St. 16. A single specimen. 



I.- 4. CiTHNA ADAMSi^ Jeffreys. (Plate XX. fig. 10.) 



Shell having the shape of a Helix, nearly globular, thin, semi- 

 transparent, and glossy : sculpture none except the umbilical ridge ; 

 colour white : spire rather short : ivhorls 4i, convex, the last occupy- 

 ing more than two thirds of the shell, and the others being in the 

 same relative proportion ; apex slightly twisted : suture very deep : 

 mouth circular, bluntly pointed at the base : outer lip thin, folded 

 partly over the umbilicus : inner lip adhering to the pillar : umbilicus 

 small and narrow, enclosed by a sharp and nearly semicircular 

 ridge ; perforation scarcely perceptible. L. 0'062o, B. 0'075. 



1 Encircled. ' Keeled. 



3 NaiHcd in honour of the memory of the late eminent malacologist Mr. Arthur 

 Adams. 



