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 posterior border 
of the nasal fossae ; the length of the latter less than their 
distance from the orbits. Praefrontal 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, c Zootomie,’ 
pi. cxliv., as that of Iguana tuber culata. 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 
Iguanidag, viz. between frontal and parietal (nearly all the 
genera), in the frontal ( BasiUscus , Corythophanes) , or in the 
parietal [Chamceleolis , Anolis). Xiphocercus 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 characters ally it to Acan - 
thodrilus y e. g. the two pairs of cylindrical and convoluted 
prostates and the condition of the nephridia. 
In 1889 Dr. Michaelsen, of Hamburg, described a worm, 
under the name of Benhamia rosea. f , which in some respects 
* Quart. Journ. Micr. Sci. xxvii. 
t Jahrb. d. Hamburg*, wiss. Ansfalten, vi. 
