Dr. G. C. Wallich on an undescribed Form 0/ Amoeba. 287 



apical groove. Head small, depressed, with the snout of mode- 

 rate length, subtruncated in front ; rostral shield rather broader 

 than high ; loreal not quite twice as long as high ; praeorbital 

 reaching to, or nearly reaching to, the vertical; two post- 

 orbitals ; nine upper labials, the fourth, fifth, and sixth of which 

 enter the orbit; temporals 1 + 2 + 2; occipitals rounded, each 

 with a larger rounded scale behind; six lower labials are in 

 contact with the chin-shields. Eye rather large, ^^-ith round 

 pupil. Body very slender, compressed ; tad very long, angular. 

 Ventral shields 165, angularly bent on each side, the central 

 portion being not much broader than long; anal bifid; sub- 

 caudals 153. The posterior maxillary tooth is the longest, not 

 grooved, and is separated from the others by a short interspace. 

 Above uniform metalhc brownish-green, below greenish ; scales 

 on the back narrowly edged with black ; one of the specimens 

 has blackish dots on the crown of the head. No band either on 

 the side of the head or of the body. 



This species would enter the subgenus Uromacer of Dumeril 

 and Bibron. 



The British Museum possesses two examples of this species, 

 one from Demerara ; the origin of the other is not known. The 

 latter is 32 inches long, the head measuring 7 hues, and the 

 tail 13i inches. 



XXXIII. — On an undescribed Indigenous Form 0/ Amoeba. 

 By G. C. Wallich, M.D., F.L.S., &c. &c. 

 [Plate VIII.] 

 The occurrence of an undescribed variety of Amoeba in the 

 immediate vicinity of the metropolis is of interest both on its own 

 account and from the indication it affords that the study of our 

 indigenous Rhizopodal fauna is still unexhausted. The variety 

 in question was recently obtained, io considerable abundance, 

 from the ponds on Hampstead Heath ; and inasmuch as every 

 specimen examined by me has presented the very singulai* cha- 

 racters to which I am now about to draw attention, there is every 

 reason to believe that these are normal, although perhaps not 

 permanent in their nature. 



According to the descriptions of the commoner forms — as, for 

 example, A. princeps, A. diffluens, or A. radiosa* — it would ap- 

 pear that the sarcode substance is uniformly differentiated into 

 " endosarc " and " ectosarc." In other words, setting aside the 

 elementary organs which may be said to be shadowed forth by 

 the contractile vesicle, the nucleus, and the protoplasmic granular 



• It will, I think, eventually be found that all these are mere transitory 

 phases of one and the same species. 



