1891.] OF PLEUROTOMARTA FROM TOBAGO. 485 



The next discovery of Plexirotomaria was in 1861, when a single 

 imperfect s}>ecimen of another species came to light. This was 

 described as PL adnnsoniana in the ' Journal de Conchyliologie ' for 

 that year (p. 163, pi. v.). This example was 80 millimetres in 

 width and 74 in height. Another more perfect specimen of this 

 species was taken near Guadelupe, and described in Journ. de Conch. 

 1882, p. 12, pi. i. This one was 85 millimetres in height and 91 

 in diameter. 



It is to this species that the Tobago shell is to be referred. Besides 

 the two examples named above, three others are known. 



Two other living species of Pleurotomaria have been described — 

 namely, PL beyrichi in 1877 and PL rumphii in 1879. The former 

 was found in Japanese waters, and of it four examples are known. 

 The latter is stated to be from the Moluccas, and only a single speci- 

 men is known. Consequently, according to the enumeration given 

 in Woodward's paper, there were up to the present time thirteen 

 specimens of recent Pleurotomaria in existence, belonging to four 

 species. The Tobago specimen is therefore the sixth of the species 

 and the fourteenth of the genus known as recent. 



The dimensions of PL quoyana and PL adansoniana have already 

 been given: those of the other two species are indicated below : — 



Height. Diameter. 



PI. rumphii 170 mm. 190 mm. 



PL beyrichi 82 „ 83 „ 



The dimensions of the present specimen of PL adansoniana are as 

 follows: — Total height 150 mm.; greatest diameter 160 mm.; height 

 of aperture 50 mm. ; width of umbilicus 20 mm. ; length of fissure 

 220 mm.; width of fissure 5 mm. This, therefore, is the second in size 

 of the specimens of recent Pleurotomaria in existence, being, in fact, 

 very nearly as large as the unique specimen o? PL rumphii, and leaving 

 all the other known examples of the genus a long way behind. The 

 coloration consists of a number of flames or irregular more or less 

 zigzag spots of flesh-red passing into orange, arranged on a ground 

 of very pale flesh tint. The apex is finely pointed, yellow, and 

 almost smooth. When viewed through the funnel-shaped umbilicus 

 and held to the light, it appears almost transparent. The supra- 

 median fissure occupies the larger half of the contour of the shell. 

 The characters generally correspond very closely with those given 

 in the ' Journal de Conchyliologie,' 1882, p. 12. The colour of our 

 specimen would appear, if we may judge by the figures, to be paler 

 than the previous examples. It is in almost perfect condition, and 

 looks as if when found it had had the soft parts in place. It is 

 merely slightly house-worn, as an article which had been kept as a 

 drawing-room ornament for several years would be. 



As has been noticed, the habitat o? Pleurotomaria is in deep water 

 on rocky bottoms. Consequently it is probable that recent shells of 

 this genus will always be rare ; for not only is it difficult to procure 

 shells living in such conditions, but the conditions themselves are of 

 verv restricted occurrence. 



