VOL. XVII.] PHILOSOPHICAL TRANSACTIONS. 501 



This description will be more easily apprehended by the first figure, fig. 4, 

 pi. 12, where A denotes the beam, B the bail of the poise, CC the neck, D 

 the mark to which it sunk in fresh water, EE the cistern or vessel containing 

 the water, F the scale wherein the weights to counterpoise it were put. 



Three Queries relating to Shells, proposed by Mr. Samuel Dale, and answered by 

 Dr. Martyn Lister, R.S.S. N° I97, p. 641. 



The Queries. — 1. What are the entalia of the shops; by what authors de- 

 scribed ; under what names ; and how they differ from the dentalia ? — 2. Of 

 what shell is the blatta byzantina,* the operculum or lid ? — 3. There are divers 

 sorts of purpuras among authors, which is that of the shops ? Likewise, which 

 sort of buccina and umbilici marini ought to be used in the shops ? 



The Answer to the Three Queries, by Dr. Lister. — 1. As to the entalia, I do 

 not remember to have seen any thing in the shops under that name. The 

 descriptions of the dentalia in Scroder, are very faulty ; and both those and 

 the entalia by him should seem to be the two species of dentalia, which are 

 figured. By me the dentalium being that which is commonly, and in plenty, 

 found about the island of Guernsey, and elsewhere upon our coast, and the 

 same with that found in the Mediterranean. It is a long, slender, round pipe, 

 a little bending and tapering, hollow and open at both ends, without any crack 

 or flaw, naturally white at one end, and usually a little reddish ; very smooth 

 and polished on the outside, and, from thence and the figure, called a dog-like 

 tooth. The entalium, or other species of the dentalia, is much longer and 

 thicker than the former, but much alike in other respects, save that this is 

 streaked with high ridges, and mostly of a greenish colour. This species I 

 guess to come from the Indies. Note, that any thing that is wrought into, or 

 channelled, is in the modern Italian called an intaglia ; whence I believe, and 

 the nearness of the word dentalia, arose those distinctions of names. 



2. To the second query ; I take the blatta byzantina to have succeeded the 

 unguis odoratus, and to have been brought into the shops in its stead. In the 

 time of Dioscorides the best was brought from the Red Sea, viz. the palest and 

 fattest; the blacker and less from Babylon or the Persian Gulf; but it seems 

 that later times took up with those found about Constantinople ; whence the 

 present shop blatta had its name. The name of blatta is given to this oper- 

 culum, I guess, from its being of a dark hair colour, as the common blatta 

 pistinaria, so common in London, is ; also this being a broad, thin, flat beetle, 

 like the cover. It is true, that Dioscorides says, the unguis was an operculum, 



• • The blatta byzantina is, according to Linnaeus, the operculum of the strombus lentiginosus. 



