THE COMMON BRITISH STURGEON. 11 



two first-named have, moreover, fringed barbels, characters 

 which have been attributed to no British Sturgeon. In 

 the other three groups, Antacei, Sturiones, and Husones, 

 the ridges of the dorsal shields are pointed in the middle, 

 and slope down anteriorly and posteriorly. These groups 

 are further characterized as follows : 4. Antacei, having 

 simple and not fringed barbels, a rudimentary mandibular 

 lip, the skin between the rows of body-shields studded 

 with stellate ossicles, and the snout short and broad. 5. 

 Sturiones, having a swollen posterior lip, contracted in 

 the middle, simple barbels, and the skin between the rows 

 of body-shields granulated by blunt ossicles. 6. Husones, 

 having the mandibular lip divided in the middle ; flat, 

 tape-like barbels, and the skin roughened by pointed 

 ossicles. The species are distinguished from each other 

 by the relative positions of the osseous centres of their 

 principal cranial shields. With respect to the value for 

 this purpose of the form of the shields, Dr. Ball says : 

 " I have collected many specimens, and I do not think 

 that the broadness or sharpness of the nose is a specific 

 distinction, as no two of my specimens can be said to 

 agree in the shape of that member, nor in the arrange- 

 ment of the scales on it and on the head. A classifica- 

 tion of the variations of my numerous examples will 

 reduce the British Sturioj Thompsoni and latirostris to a 

 single species." Mr. Thompson also observes that " the 

 precise form of the bony plates on the head is of no value 

 as a specific character, neither is the breadth of the 

 snout." These opinions of the Irish naturalists are 

 shared by several English ichthyologists, and the subject 

 requires to be worked out by an investigator who has 

 access to a sufficient number of examples from various 

 British localities, and an opportunity of comparing them 

 with specimens collected from the Continental rivers. 



