6 MONOGRAPH OF THE FRESH WATER III. 



In our Revision of the gam* ('<>ltii*, 1 we advanced the opinion that this species 

 would be found distinct, not knowing at that time that it had been already named. 



These were progressive steps in European ichthyology, but there still remains 

 carefully to compare with the above species, the C. gobio of England, France, Den- 

 mark, Germany, and Russia, in order to ascertain whether several species are not 

 still confounded. We have already remarked a certain disagreement on this subject 

 among authors. Cuvier makes the positive remark that the C. gobio has only three 

 soft rays to the ventral fins, whilst Dr. Richardson mentions four as belonging to 

 the English species examined by him, and which is the same as the one described 

 by Mr. Yarrell. This also has but six spinous rays to the first dorsal, and sixteen 

 soft and articulated, but unbranched rays, to the second dorsal. The assertion 

 of Cuvier, that the first dorsal of C. gobio counts from six to nine spinous rays, is 

 a fact to be verified anew : perhaps the above English species is taken into account 

 in the formula. Moreover, Cuvier says, positively, that the rays of the centre of 

 the second dorsal dichotomize at their extremity. Finally, in the C. gobio of the 

 Seine the upper rays of the pectorals are branched, whilst they are all simple in 

 the English species spoken of by Dr. Richardson. 



Should these differences prove constant, and we have no doubt they will, they arc 

 more than sufficient for specific distinction, and we are satisfied of the existence of 

 two species of Cottus in the British Islands, for we find mentioned sometimes three 

 and sometimes four rays to the ventrals of the so-called C. gobio. This character, 

 which proves safe among American species, will no doubt be a sure guide in a 

 critical review of the European ones. We have seen a mutilated specimen of an 

 English Miller's Thumb with evidently branched pectoral rays, therefore differing 

 from the one alluded to by Sir John Richardson. The Miller's Thumb from the 

 Seine again differs from that of the Danube. Those of the Rhine, of the Rhone, 

 and the south of France generally, deserve a special attention, as well as the one 

 mentioned by Reisinger in his Ichlltyolmjin} Hungarice, which seems to attain a very 

 large size. In fact, the Cottoids of all the European and Asiatic rivers and lake's 

 should be compared directly. It is only after this is done that we shall be prepared 

 to establish safe comparisons between the species of one continent and another. 



Now, if we recapitulate the European species, we find five of them to be well 

 determined and named. In addition, we have two species in England as alluded 

 to above, which are distinct from C. gobio of the Seine; thus giving seven species. 

 Then, in central Europe several other species will probably be found distinct. 

 C. jxi >!/!>]' a* must be compared with the giJiIo of Reisinger, of the Danube. Be it 

 remembered that the latter spawns in .March and April. A comparison of the 

 C. gobio from the Seine (spawning in May, June, and July) with that of the south 

 of France, and then again with that of the Swiss lakes and the rivers of conti- 

 nental Europe, would no doubt add to the number of species. It would be inte- 



liir,: to know whether the Miller's Thumbs exist southwards of the Pyren* 

 in Spain and Portugal, as well as in Greece and Asia Minor. 



M. moires de la Socirtr Il.-lv'iii|iic ilos Si-ii/nccs Naturclles, vol. xii., 1851. 



