chap, xviii.] MEDIAN DIVISION : MISCELLANEOUS. 



457 



probably very rare. Packard, A. S., Mem. Bost. N. II. S., 1872, n. p. 

 201, .$7. 

 712. Palamnaeus borneensis (Scorpion) : specimen in which the 

 terminal poison-spine was double, as 

 shewn in Fig. 144. The two halves 

 were not quite equal and there was no 

 opening of a poison-gland on the shorter 

 spine. This specimen, which is in the 

 Brit. Mus. was kindly shewn to me by 

 Mr R. I. Pocock. 



Chirocephalus £ : specimen hav- 

 ing the generative sac with two horns 

 instead of one. [Normally there is only 

 one such horn which forms a median 

 downward prolongation of the ovisac. 

 No further description.] Provost, B., 

 Mem. sur les Chirocephales, p. 232 ; in 



71; 



Jurine's 

 1820. 



Hist, des Monocles. Geneva, 



Fig. 144. Double poison-spine 

 of a Scorpion {Palamncem borne- 

 ensis). I. From dorsal side. 

 II. From ventral side. ??, the 

 spine which bore the openings of 

 the poison-glands. 



714. Buccinum undatum. A number of specimens were formerly obtained from 

 Sandgate in Kent 1 , having the operculum double. Sometimes the two opercula 

 were separate, sometimes united. Many specimens of this variation are in the 

 collection of Dr A. M. Norman, who kindly shewed them to me. The shells and 

 opercula alone remain and consequently it is not now possible to determine the 

 position of the line of division relatively to the morphological planes of the animal ; 

 but, from the fact that in several instances the two opercula were related to each 

 other as images, it seems likely that the division was in the longitudinal median 

 plane, though this must be uncertain. Moreover in one of Dr Norman's specimens, 

 from the fragment of dried flesh adhering, it appeared that the apex of the foot 

 might have been bifid. Four cases are shewn in Fig. 145. In two of them (I and 

 II) there is a fairly close relation of images, while in III this relation is less clear 

 and in IV it is practically destroyed, though it is of course quite possible that this 

 may be the result of unequal growth. Several of these opercula are much contorted 

 and without any very definite shape. 



II I 



w. 



HE 



Fig. 145. Cases of duplicity in operculum of Buccinum undatum, from 

 specimens in the collection of Dr A. M. Norman. I and II nat. size. Ill and 

 IV enlarged. Ill and IV were kindly drawn for me by Mr J. J. Lister. 



1 See Jeffreys, J. G., Ann. Mag. N. H., 1860 (2), p. 152. 



