TIRODESMUS.—EURYURIN &. 147 
Dorsal area convex in the middle. eels horizontal, with pore remote from the margin ; anterior and 
posterior borders irregular or armed with tuberculiform teeth, not serrulate ; lateral border usually with 
four or five larger subspiniform teeth and some smaller tubercles; two of the teeth are upon the posterior 
angle, which is acute but never actually spiniform. First tergal plate with keels well developed, pro- 
jJecting forwards and outwards, so that the widest point of the plate is well in advance of its middle ; 
posterior border of the keel, as of all the rest except of the 18th and 19th, concave, at all events 
externally. Caudal process quadrate, with parallel sides and irregular tubercular convex posterior 
border. Anal sternal plate with large tubercles. Sternal areas rather narrow, their width about equal 
to the length of the second segment of the leg and less than half that of the third in the mid-region 
of the body ; not distinctly tubercular but transversely and longitudinally hollowed. 
3. Like the 2, but smaller, with keels relatively larger and higher, those at the posterior end being more 
strongly raised. Sternum of third segment with triangular tubercle, which is also present in 2. 
Length, 2, 95 millim., width 16. 
» 6, 87 ,, » 15. 
Hab. Costa Rica, La Palma! (Tristan & Biolley), Las Delicias (Biolley), Cariblanco 
(Lankester'). — 
The coarseness of the granulation and the number and development of the lateral 
teeth on the keels are subject to considerable individual variation in this species. 
I believe the specimens above described to be accurately identified. Nevertheless it 
must be pointed out that the shape of the keel of the tenth segment is, in all my 
examples, very different from that of the tenth segment of the type-specimen, as 
depicted by Carl. Since, however, tnis figure does not agree with the description as 
regards the position of the pore, which is much too near the sides of the body, I feel 
justified in assuming that it may be inaccurate in other respects and have its lateral 
border much too long and its anterior border insufficiently oblique. It gives very 
little idea of the peculiarity in the shape of the keels exhibited in my specimens, 
which must be specifically distinct from TZ. dcolleyi, if the figure in question is 
correct. 
Subfam. HURYURINA. 
With the possible exception of Aphelidesmus, which appears to link the typical members of this subfamily 
with the Chelodesmide, the two genera here referred to the Euryurine form a natural group, differing 
from the Platyrachine mainly in the fact that the lateral margin of the keel is smooth, thickened, 
differentiated from the rest of the upper surface of the keel, and carries the pore, which does not present 
so markedly the cannon-mouth appearance so noticeable in the Platyrachine. 
Distribution. Eastern area of Oriental Region; Southern States of North America ; 
Jentral America and northern area of South America. 
The three Central-American genera here admitted may be distinguished as 
follows :— 
a. Dorsal surface of segments more or less strongly sculptured ; phallopod 
simple, terminating in one or two accessory processes in addition to the 
seminal stile; caudal process squared or rounded. 
b. Anal sternal plate with its posterior margin straight or concave, not 
produced between the setiferous tubercles AMPLINUS. 
U2 
