414 Dr. W. B. Benham on the sphenoid rather elongate and much constricted behind the basipterygoid processes, intermediate between Metopoceros and Ctenosaura. 7. Ctenosaura^ Wiegm. — Lateral teeth with three or four cusps. Prsemaxillary extending as far as the ])Osterior border of the nasal fossae ; the length of the latter less than their distance from the orbits. Prsefrontal not entering the nasal fossa. Postfronto-squamosal arch slender, at least as long as the orbit ; postfrontal longer than deep. Transpalatine not in contact with palatine. Basisphenoid elongate and much constricted behind the basipterygoid processes. The skull of Cyclura is figured by Briihl, * Zootomie,' pi. cxliv., as that of Iguana tiiherculata. An excellent figure of the skull of Metopoceros is given by Cuvier, Oss, Foss. v. pt. 2, pi. xvi. figs. 23-26. In the figure published by Giin-ther, Trans. Zool. Soc. xi. pi. xliv., the parietal foramen is represented, through an error of the artist in the drawing of the sutures, as in the frontal bone, whilst, as in other Iguanas, it is situated between frontal and parietal. The three possible positions of the parietal foramen are to be found in the family Iguanidaj, viz. between frontal and parietal (nearly all the genera), in the frontal {Basihscus, Corythophanes) , or in the parietal [ChamceleoUs^ Anolis). Xiphocei'cus and Norops, though so closely allied to Anolis, have the foramen between frontal and parietal. L. — The Genera Trigaster and Benhamia. By W. Blaxland Benham, D.Sc, Assistant to the Jodrell Pro-fessor of Zoology, University College, London. In 1886 I described an earthworm from the island of St. Thomas, West Indies, its most remarkable peculiarity (at that stage of our knowledge of earthworms) being the posses-sion of three separate gizzards ; to this worm I gave the name Trigaster Lankesteri *. Its other chai'acters ally it to Acan-thodrilus, e. g. the two pairs of cylindrical and convoluted prostates and the condition of the nephridia. In 1889 Dr. Michaelsen, of Hamburg, desci*ibed a worm, under the name of Benhamia roseat, which in some respects * Quart. Journ. Micr. Sci. xxvii. t Jahrb. d. Hamburg, wiss. AnstaUen, vi.
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