156 DIPLOPODA. 
a'. Antero-lateral tooth of keels smaller, not long and acute, and not projecting 
so far laterally as the second and third teeth; lateral border of keels of 
second segment with three teeth . . 2. .. ., 
oe (? in woodianus.) 
6. Antero-lateral tooth of keels, except at posterior end of the body, 
moderately large but truncate; very few tubercles on the keels. . . . Airsutus. 
4’. Antero-lateral tooth of keels a minute sharp denticle; keels more 
tubercular than the median area of the segments . . . . . . . . woodianus. 
1. Peridontodesmus flagellatus, sp.n. (Tab. X. figg. 4-4 9.) 
2. Colour nearly uniformly testaceous or yellow-brown. Head beset with short hairs inferiorly ; antenne 
similarly clothed distally. First tergal plate with large horizontal keels, its anterior border with a row 
of eight small setiferous tubercles increasing in size externally and passing into the teeth of the antero- 
lateral border of the keel, of which there are five, the posterior being the smallest ; posterior border of 
the keel directed forwards and outwards ; the median area of the plate only lightly convex and bearing 
three rows of tubercles in addition to those on the anterior border. The rest of the segments very 
similar in form to one another; each with three rows of tubercles, the posterior row being on the 
posterior border; a shallow transverse sulcus lying between the first and second rows, on all but the 
second, third, fourth, and nineteenth ; on the keels there are only about four or five tubercles continuing 
the anterior and median rows; the median area of the segments lightly convex ; the keels large, set high 
on the sides, nearly horizontal ; from the second to about the sixth directed slightly forwards, but the 
forward inclination less and less marked towards the middle of the body, those of the mid-region being 
transverse ; from the 16th to the 19th directed more and more backwards; the keels at the posterior 
end more squared or rhomboid than those at the anterior end, which are wider than long and narrowed 
externally, except on the second; in all cases the keels as long as the segment, with the anterior border 
straight or becoming lightly convex in the posterior half of the body; the anterior angle well marked, 
acute in front, squared in the mid-region, and obtuse posteriorly ; the second with well-marked posterior 
angle; its lateral edge armed with four strong teeth, the first and fourth being respectively upon the 
anterior and posterior angles ; its posterior border also with four teeth, whereof the internal is smaller 
and lobate or subtubercular; from the third to about the tenth the lateral and posterior teeth form a 
coutinuous curved series ; on the poreless keels there are three strong lateral teeth and four posterior 
teeth, the latter becoming gradually smaller and more rounded and lobate internally ; the second and 
third lateral teeth with a supplementary tooth on most of the segments ; on the pore-bearing keels there 
are two lateral teeth in front and a large subdivided tooth on the posterior angle, which becomes more 
and more acute and produced from about the 16th to the 19th; three teeth on the posterior border of 
the 17th, two on the 18th, and one on the 19th, but the teeth on these keels all smaller than those 
of the segments preceding them, and the anterior with a supplementary denticle. Pores conspicuous, 
normal in number, situated above the edge and rather more than their own diameter internally to and in 
front of the angular notch dividing the large tooth into its two moieties. 
3. Like the 2, but smaller and with the keels a little larger and more horizontal; and, at least in the 
specimens examined, there is no anterior supplementary tooth on the second and third teeth on the lateral 
border of the keels. For structure of the phallopods, reference may be made to the generic diagnosis and 
to the figures. 
Length of 2 9 millim., width 2; length of g 7 millim., width about 1:5. 
Hab. Guatemaua, Cholhuitz (Stol/). 
2. Peridontodesmus hirsutus, sp. n. (Tab. X. figg. 5, 5a.) 
2. Colour (in alcohol) dark blackish-green, fading when dry to pale olive-grey, without the yellowish or 
brownish tinge of P, flagellatus, Very similar to the latter, but larger, and differing in the following 
particulars : the keels are narrower and less lamellar, those of the second are only armed laterally with 
