MollusK-s. 771 



within the observation of British naturalists to have received so many 

 names as the fancies or mistakes of authors have affixed to the more 

 common species. But to avoid all errors in reference, it is necessary 

 to say, that under the name Natica glaucina is meant that which by 

 Pennant is denominated Nerita glaucina, and, it is believed, also by 

 Montagu; by Fleming, Natica glaucina. Professor Edward Forbes, 

 as quoted above, terms it Natica monilifera, from a supposition that it 

 may be the shell so called by Lamarck ; and the same is adopted by 

 Macgillivray, ('Molluscous Animals of Aberdeen,' &c. 125). 



In September of the present year (1844) I obtained a specimen of 

 Natica intricata, from Penzance ; and this I supposed to be the first 

 I had ever seen. But in the course of the same month I obtained a 

 much larger specimen from Plymouth Sound ; and a comparison of 

 this pair with a fine specimen of the more common N. glaucina, will 

 enable me to give a measurement and description, sufficiently precise 

 to fix the identity of the rarer species. 



The smaller specimen of N. intricata here referred to, measures 4^ 

 of an inch in its longest diameter ; but the larger, which was 44 in its 

 longest diameter, and 44 m its shortest diameter, afforded a closer 

 comparison with N. glaucina, my largest specimen of which is 4-1 by 

 44*in these diameters. The latter, therefore, is a rounder and more 

 compact shell, the greater comparative length of N. intricata being 

 obvious on inspection. They differ also in the arrangement of the 

 whorls, as well as in their number ; which, in N. glaucina, is clearly 

 six, but in N. intricata no more than five can be ascertained. In N. 

 glaucina the second and the smaller whorls are more inflated, and form 

 a higher spire, the decreasing line of separation having a regularly 

 circular sweep ; whereas in N. intricata, besides that the whole is 

 much more depressed, the spire is not placed in the centre of the 

 whorl, but inclined to the superior side. Another distinguishing mark 

 is the form and situation of the umbilicus ; which in N. glaucina is a 

 simple ascending cavity, in a degree intruded on by a single porcella- 

 neous band, which proceeds from the columella. In N. intricata this 

 band is divided so nearly into two, that the connexion is only by a 

 narrow slip ; and the cleft or separating gap, which in the smaller 

 specimen is rounded, and in the larger square, exposes the umbilicus 

 above the columella, and therefore passes directly inward, instead of 

 obliquely upward as in N. glaucina. The pillar thus becomes ex- 

 posed, uncovered by the band on one side, and the body-whorl on 

 the other, in a manner to be highly characteristic of the adult state. 

 The inferior portion of the band does not stretch fully across to the 



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