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. 



