HUXLEY, ON THE MOUTH OF THE SCORPION. 253 



The structure of the parts which I have observed in a large 

 species of Buthus may be described as follows : 



The "buccal appendage" of M. Blanchard is a vertically 

 elongated, laterally compressed, cushion-like prominence, 

 broad and rounded above, where it is marked by a slight 

 median ridge, slightly concave from above downwards in 

 front, and narrowed below (PI. XII, figs. 1, 2, 3 b). Its 

 anterior and lateral surfaces are covered with fine, short hairs, 

 which form a projecting pencil at its anterior inferior angle. 

 There is no aperture whatsoever above this body, between the 

 chelicerae; but, below and behind it, the aperture of the 

 mouth, large enough to admit the head of a fine needle, can 

 be very easily found. I entertain no doubt, therefore, that 

 this " buccal appendage" is a true labrum, and, indeed, in all 

 essential respects, it is exactly like that part in the Crustacea. 



The convex lower surface of the labrum bounds the mouth 

 in front, while behind, it is limited by a transverse thicken- 

 ing of the chitinous integument, which appears to represent 

 the sternum of the mandibular somite (fig. 4 6). The mouth 

 opens into a very curious pharynx, formed by a delicate 

 outer investment, and a strong inner chitinous lining. 

 Viewed laterally, this organ (c) has the shape of a pear, 

 its broad end being uppermost, and its long axis directed 

 obliquely upwards and backwards, in such a manner, that 

 the broad upper end lies in the middle, between the prongs 

 of the fork- like apodeme, which M. Blanchard has de- 

 scribed. Viewed from above or below, however, the 

 pharynx appears to be very narrow, indeed, almost linear, 

 in consequence of its very peculiar form, which is displayed 

 in the section, taken transversely to the longitudinal axis 

 and perpendicularly to the vertical plane represented in fig. 5. 

 The cavity of the sac is here seen to be triradiate, while 

 its walls are very closely approximated, so as to leave but 

 a slight interspace. The narrow band which joins the 

 two lateral walls below and behind is slightly excavated, so 

 as to present a convexity towards the cavity of the pha- 

 rynx. The tw r o shorter rays of the sac are turned upwards 

 and outwards; the third longer ray is directed vertically down- 

 wards. The oesophagus, an exceedingly delicate and narrow 

 tube, comes off from the posterior wall of the vertical ray or crus 

 of the pharynx, just above the mouth ; and, widening, passes 

 backwards and upwards, into the dilatation which receives the 

 ducts of the so-called salivary glands (e) . Just above the aper- 

 ture is a rounded projection (fig. 6 p), which I suspect may 

 act as a sort of valve, when the sides of the pharynx are diva- 

 ricated, by more or less completely occluding the oesophageal 



