Dusky blue above, silvery beneath: dorsals contiguous.
From eight to ten inches.
Differs from the P. fluviatilis, principally in having the two dorsals contiguous, or with only a very small space between: the first commences at about, or a little before, the middle of the entire length; the second at exactly two-thirds of the same: the vent is, relatively, a little further from the extremity of the tail; the body is also somewhat thicker in proportion to its length. In all other respects, including colours, armature of the mouth, etc, the two species are identical.
This species is evidently the P. Planeri of Cuvier and Nilsson, but not of Bloch and Blainville. That of Bloch, Cuvier thinks is only the young of P. fluviatilis. It is probably also the species described by Willughby under the name of Lampetra parva, in which he expressly speaks of the two dorsals being contiguous. Willughby, however, erroneously considered it as the Pride of Plot, a circumstance which has led to some little confusion in the works of later authors with respect to the synonyms of this last fish. Whether the P. Planeri be common in this country I am not aware. My specimens were given to me by Mr. Yarrell, who obtained them from a brook in Surrey. The same gentleman has since received it from the Tweed.
West. Isl. vol. ii. pp. 186, 187. pl. 29. f. 1.
Under the above name, Dr. Mac Culloch has described a species of Petromyzon, which he considers distinct from those hitherto noticed by naturalists. He observes that " in size it approaches to the P. fluviatilis, which it also resembles in the proportion and disposition of the fins; but that it differs materially in the absence of the annuli, in the greater number of the teeth, and in the number and forms of the bony bodies which surround the opening of the throat." This fish was found adhering to the back of a gray gurnard on the Eastern shore of Jura: the specimen was not preserved. Dr. Fleming does not seem to allow that it is specifically different from the P. fluviatilis*, an opinion in which I feel inclined to join.