Mr. E-. I. Pocock on the Genus Theatops. 283 



In interpreting the malformation just described, I venture 

 to follow a suggestion of Dr. Giinther, and regard the bilateral 

 symmetry of the dentition as merely obscured by a partial 

 subdivision of two of its elements. The three outer rows of 

 teeth on each side (II, III, IV) are normal and approxi- 

 mately symmetrical. The first lateral row of one side must 

 thus have become subdivided ; and as the large mesial teeth are 

 decidedly unsymmetrical and do not quite occupy the middle 

 part of the dentition, their extremities on the abnormal side 

 also seem to have been detached. Indeed, it will be noticed 

 that if the first two of the abnormal lateral rows (O h, O c) 

 could be connected with the very broad teeth, the latter would 

 be precisely median ; and the manner in which the length of 

 the teeth of the second of these series varies with the differ- 

 ences in the length of the broad teeth seems to prove that the 

 homology denoted by the lettering is correct. The three 

 rows marked I a, I ^, I c, taken together are exactly equal 

 in breadth to the first row of the opposite side, and may thus 

 be regarded as its equivalent. 



No specimen hitherto described appears to exhibit malfor- 

 mation equal to that of this unique dentition ; but it may be 

 added that Sir Richard Owen * has already noted the sub- 

 division into two parts of the first lateral series of teeth in 

 the East-Indian Rhinoptera javanica. 



XXXV. — On he Genus Theatops. By R. I. PocoCK, 

 Assistant, Natural- History Museum. 



[Plate XVr. figs. 6-10.] 



Whilst reading in the ' Entomologia Americana,' vol. iii. 

 no. 4, a paper entitled " The Scolopendridee of the United 

 States," by Lucien M. Underwood, Ph D., my attention was 

 attracted on page 65 by a footnote which suggested to mc 

 the advisability of publishing the present paper. This foot- 

 note I quote verbatim : — 



" The genus Theatops has had a strange history, and after 

 all its vicissitudes may as well be consigned to oblivion. It 

 was first described by Say (1821) as Cnjptops 2Jostica, from 

 Georgia and East Florida. Newport in 1844 established the 



* ' OcloDtogTaphy,' p. 46, pi. xxv. fig-. 2. 



