ACIPENSER (mELTXI. 391 



Acipenser ruthenns. Variety gmelini (F. & H.). 



We have already spoken of the liability to variation of the Acipenser 

 rntJiciiHN, and Dr. Giinther has classed the Acipenser gmelini as a further 

 illustration of the capacity of the species for change of character, but the variety 

 is so marked in many structural details that we have considered it necessary 

 to briefly describe it (Fig-. 180). 



It is distinguished by its broad triangular rostrum or snout from the 

 Sterlet, which it resembles in form of body, and in the thick compressed 

 lozenge-shaped lateral shields. The head measures one-fifth of the entire 

 length, the height of the body is rather more than its thickness, and this is 



Fig. 180. ACIl'ENSEK HVTHEXU8, VAR. GMELINI (FITZINGEll AXI) HECKEL). 



about one- eighth of the total length. The arched forehead rises somewhat 

 abruptly from the snout, and the elevation continues to the back of the head. 

 The greatest height of body is measured from the first dorsal shield to the base 

 of the pectoral fin. According to Heckel and Kner's figure (Fig. 181), there 

 is considerable difference in the form and proportions of the cephalic scutes. 

 First, the supra-occipital scute is small and entirely separated from the epiotic 

 scute in contact with the long parietal scutes. Secondly, the parietal scutes 

 are not divided in front because no distinct ethmoid scutes are developed. 

 Thirdly, the post-frontal scutes, which are external to the frontal, and notched 

 out for the orbit, are pointed behind, and extend back as far as the frontal scutes 

 with their points external to the squamosal scutes, instead of penetrating into 

 those ossifications. There are no distinct pre-frontal or nasal ossifications, and 

 the frontal plates in front are not sharply distinguished from the compact 

 ossifications which extend over the snout. All the sculpturing on the shields 

 is finer than in A. rutlienus. 



The pores on Ihe under side of the head are similar to those in the Sterlet, 

 as are also the rows of pores in the cephalic canals. The middle bony ridge on 

 the under side of the rostrum decreases gradually in width from its extremity 

 towards the mouth, and is completely broken four times, making four round 



