seems to me, to be considered even subgenerically related, while specifically this species must certainly stand alone. This is especially evident when we consider (4) That one of the two diagnostic characters of the subgenus Ctenopterus depends upon the comparison of the lengths of the first three pairs of legs, the particular comparison
 Fig. 23 b. Stylonurus cestrotus Clarke. Second and third legs on left side. (After Clarke and Ruedemann, 1912, pl. XLIX, fig. 4.) |
being made between the first, and the second and third pairs, but in S. elegans the first pair is unknown.
Stylonurus ornatus and S. macrophthalmus are in some respects quite closely related to species occurring in the later Scottish horizons in connection with which they will be spoken of again. Here it is sufficient to note that there are no North American species which have the characters of the genus Stylonurus (sens. str.) namely, the
