Fish of the Family of Sturgeons. 271 



frontals, and two temporals. The small occipital shield is 

 almost of a ti-iangular form, with a scarcely observable longi- 

 tudinal ridge, and with its anterior acute end deeply buried 

 between the two parietals. The central points of the parietals 

 are almost opposite to the front margin of the gill-covers, and 

 appear as very slight elevations ; the interspace between these 

 central elevations is slightly hollow, like a shallow gutter, and 

 its breadth is considerably less than that of the interspaces be- 

 tween each central elevation and the con-esponding gill-cover. 

 Outside of the parietals there are the flat temporals, whose 

 central points are in a diagonal line with the central elevations 

 of the parietals. Posteriorly the parietals, as well as the 

 temporals, rest against the upper dorsal shields, which, like 

 the temporals, are completely flat. The slightly projecting 

 central points of the frontal shields are opposite to the front 

 border of the eye. On the outer side of the frontal shields 

 there are two little cavities, at the bottom of which the frontals 

 are separated from the supraciliary shields by a little narrow 

 membranaceous interspace. The interspace between the 

 frontals is partly occupied by the acute front ends of the 

 parietals, and partly by a separate odd interfrontal shield. In 

 front of the above-named shields the whole of the upper part 

 of the snout is covered with elongate lanceolate shields, 

 which gradually become smaller and thinner and more difficult 

 to distinguish. Between them, towards the margins of the 

 snout, there are skinny interspaces, mostly of irregular oval 

 shape and of various sizes, and occupied by those peculiar 

 organs which are called by Meckel " Schleimdriisen " (mucous 

 glands). 



The lower side of the snout is completely flat : only in dried 

 specimens the borders of the snout are turned inside, and give 

 it the shape of a shallow gutter. There may be seen sometimes 

 in the centre of the lower side of the snout a longitudinal promi- 

 nence, caused by a bony rib passing there. The whole of the 

 lower side is covered by a thick soft skin containing a dense 

 network of folds, in the loops of which are little pores crowded 

 together (according to Meckel the openings of the mucous 

 glands). Four completely smooth barbels, situated on the 

 lower side of the snout, are placed in a transverse, slightly 

 curved line. The outer barbels are from two to three times 

 as long as the inner, and when adpressed to the snout they 

 reach to the mouth. The interspace separating the two inner 

 barbels is almost twice as wide as that between each inner and 

 outer barbel. The outer barbels are generally close to the 

 margin of the snout : their distance from the end of the snout 

 is the greater the longer the snout ; but even in sliort-snouted 



19* 



