On a new Species of Thamnodrilus. 153 
impossible to refer it to the genus Plestochelys, although in 
its general structure it seems closely allied. It will probably 
be best to refer it to a new genus—Tholemys,—its specific 
name being Tholemys passmorei, in honour of Mr. A. D. 
Passmore, the discoverer of this valuable specimen. Possibly 
Tholemys may represent a primitive condition through which 
the Plesiochelyid passed before fusion between the pelvis 
and xiphiplastra became established. 
XIV.—On a new Species of the Oligochate Genus Thamno- 
drilus (Beddard), with Notes on Th. gulielmi. By FRANK 
K. Bepparp, M.A., D.Sc., F.R.S. 
THIS genus was originally described by myself*, subsequently 
referred to one or other of Perrier’s genera Anteus and Rhino- 
drilus, and lastly restored (by Michaelsen) to its original 
position Tt. ‘The species now number some forty-five or so, 
and all of them are dealt with by Michaelsen in the memoir 
referred to below, and (up to the year 1906) by Cognetti in 
his comprehensive work upon the Oligocheta of the Neo- 
tropical region}. The species upon which I here report 
appears to me to be new, though most nearly related to 
Th. columbianus of Michaelsen and to Th. darienanus. To 
the describer of the latter, Luigi Cognetti de Martiis, I 
dedicate the present form, and name it Thamnodrilus cognettii. 
The material for the following account I owe to the kindness 
of Mr. R. H. Burne, Physiological Curator of the Royal 
College of Surgeons, who was so good as to hand over to me 
a number of examples of this South-American worm, none of 
which were at the same time fully mature and complete in 
length. The largest and most complete individual was some 
8 inches long and 12 mm. in breadth at the broadest part of 
the body (head end). A fragment of another individual 
indicated a still larger specimen, as the clitellum was 14 or 
15 mm. in diameter, 
The prostomium is broad. The jirst two segments are 
* “On the Structure of a new Genus of Lumbricide (Thamnodrilus 
gulielmt),” Proc. Zool. Soc. 1887, p. 154. 
+t “Die Lumbriciden,” Zool. Jahrb., Abth. f. Syst. xli; 1917, p.1. I 
am greatly indebted to Prof. J. Stephenson for allowing me the use of a 
copy of this publication. 
{ “Gli Oligocheti della regione neotropicale,” Mem. R. Acc. Sci. 
Torino, pt. ii, 1906, p. 147, 
