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Show 260 DR. W. B. BEXHAM OX [Nov. 15, depends on the law of priority ; and there can be little doubt but that Megascolides australis is the " type " of Megascolides M‘Coy ; but it does not seem quite so clear as to whether the word Notoscolex or Gryptodrilus should be retained to apply to the other genus. But this thorny matter of nomenclature I regret that I have not time to discuss thoroughly. Having thus cleared the ground, satisfactorily as it seems, of the meganephric species, there remain the large series of micro-nephric species to be dealt with ; and it becomes a question whether Michaelsen's characters are good, viz. : (a) Absence or presence of meganephridia posteriorly ; and (b) A limited number (two pairs) or a greater number (up to five pairs) of spermathecee. In regard to the first, it is admitted that in many species we are ignorant as to whether the large nephridia are or are not present. In the second case, in other genera-e. g., Pheretima and Mega-scolex- the number of spermathecae has not been used as a generic character*. Since, therefore, the seven species of New-Zealand worms here described agree very closely with one another, and except in one respect differ from those species referred to Megascolides by Michaelsen, and since, too, I am not in a position to rearrange the generic characters of these allied genera, it seems to me better to erect a new genus. It may be that it is only of subgeneric rank ; but for the present less confusion will arise, I think, if we regard it as a distinct genus. The genus Tokea differs from Megascolides, as defined by Michaelsen, in the following points :- (a) The limited extent of the clitellum, in which only 4 or 5 segments are involved, whereas his minimum is six. (b) The widely separated chaetse, of which the coupling is not recognisable. (c) The form and position and size of the prostate. (d) The position of the point of entrance of the sperm-duct into the prostate-duct. (e) The existence throughout the body of nephridial funnels, although in the greater part of the worm these have no connection with the nephridia. These are truly small points of difference on which to form a new genus ; but not smaller than that on which Megascolides is distinguished from Notoscolex, viz., the presence in the former of meganephridia in the hinder segments of the body f. In my opinion, this is by no means a good line of distinction; and even * The same remark applies to the position of the last heart, utilised in diagnosing the genera by Beddard; for in Plagiocliceta and Octochcetus, as in Tokea, we find species in which it is in the 12th, and others in which it is in the 13th segment f Or, Maoridrilus from Notiodrilus, in having nephridiopores alternate, instead of in line |
