OP NEW SOUTH WALES. 247 



to say, three in a diagonal line on each side from a central tooth. 

 They are perfectly vitreous, colorless, and transparent. The central 

 tooth is long-curved and sharp-pointed, with two very small lateral 

 cusps. The first two laterals are also apparently provided with 

 cusps. The outer teeth have a broad summit, which is tridentate. 

 Thus it differs from the dental formula given after Wilton in 

 Woodward's Mollnsca (Tate's edit. 1871, p. 252), and from that of 

 Gray (Guide to Mollusca in Brit. Mus., 1857, p. 90). The tube 

 of the odontophore is so very thin that the upper membrane is 

 easily destroyed in drying. 



Eisella nana. B. t. arbicvlari, stibronica, ad periphceriam, 

 acute angulata, cinereo-virente ; Uriels longitudimalibus fuscis radi- 

 antibus; anfr. planiuscuhs ; hi fima facie plana, concentrice sulcata, 

 violarescente ; umbilico nulla. Lamarck 1822, an'm. s. verteb., 

 gen. Trochus n. 67. Alt. 12, diam. max. 16 mil. 



This species or variety, which, as I have said, takes the office of 

 female to R. aurata, differs in being a larger and more solid shell 

 with flattened smooth whorls which are seldom rugose, and seldom 

 with the regular plaits of the male variety. It is sometimes much 

 corroded and rough, and is either high and obtusely conical with 

 an obtusely angled periphery, or depressed and very acutely angled. 

 One constant feature it possesses, unless where much corroded, 

 and that is the transverse sloping brown or black lines on a grey 

 or brown ground. It has the same Urate flattened base, with the 

 smooth margin, which is common to all the species known to me. 

 The mouth has a highly polished enamel, variously striped or 

 clouded, yellow and brown, but much paler generally, and with 

 less brown than the preceding variety. It is a larger shell in 

 every way, more solid, and with a thickened base. The odonto- 

 phore is similar to the last described in the number and arrange- 

 ment of the teeth, but they are less crowded and longer. ' It is 

 longer and broader, and like the preceding, a tube. 



Though the above differences are plainly marked in the extremes 

 of both varieties, yet it must be admitted that gradations from one 

 form to the other may be found. The spiral lirse with plaits in 



