232 S. H. SCUDDER OX THE FOSSIL 



parison of specimens in wliich the anterior segments only were preserved, with others 

 which he considered posterior segments ; but every specimen I have seen either is or is not 

 smooth throughout tlie whole length of the fragment, and there are quite a number of 

 fragments in which more than half the body is preserved ; this distinction is the one upon 

 which I would base my division of these millipedes into two genera. In one (for which 

 the name of Xylobius may be retained, since it comprises the larger number both of spe- 

 cies and of specimens) the segments composing the body are broken up by longitud- 

 inal sutures into little quadrangular plates, of varying form and proportion, which, 

 for want of a better name, I have designated below as frusira, and which, to the best 

 of my knowledge, are wanting in any li^nng Myriapoda.^ In the other, which may 

 be called Ai'chiulus, the segments are apparently composed mainly of one unbroken 

 piece, as in recent myriapods. Other distinctions between these groups will doubtless 

 be found ; but the imperfect preservation of the fossils — not one of them approach- 

 ing completeness — forbids their present discovery. In the meantime it does not seem 

 mrreasonable to consider this featm-e alone in the structm-e of the segments of sufficient 

 importance to separate the groups generically. 



Of the genus Xylohius four species may be distinguished among the remains from Nova 

 Scotia. For the species best represented both in nimibers and in the character of the 

 specimens, I have retained the original name apphed by Dr. Dawson. 



Xylobius sigillariae Daws. 



There are no large fragments of this myriapod and but few that throw any hght upon 

 the form of the terminal portions of the body ; the specimens are usually more or less 

 coiled, and the largest, Avhich is 28 ™"- in length, is curved in the form of a semi-circle. 



1 Mr. Edward Burgess lias called my attention to a myriapod, succeed each other in regular lines from one end of the 



Spiroslrephon lactarius (Say) Brandt, which presents a some- body to the other, and thus form strong longitudinal ridges 



what similar appearance ; the segments in this peculiar which follow those of the first segment. The ridge formed 



chilognath bear frequent, longitudinal ridges, very elevated by the median dorsal carina is slightly pronounced; on 



and strongly compressed, the altitude of every other one each side of it are two stronger ones ; the second lateral 



being double that of the intermediate; the segments are carina projects more strongly than the others, and arises on 



divided by these ridges into quadrilateral sections of much each side of a strong, black, cylindical tubercle, which is 



the same proportions as the frustra of Xylobius sir/il- truncated at its summit, where the foramen repugnatorium 



laricB Daws. ; but since these sections are perfectly con- opens, and followed behind by another smaller sharp tu- 



tinuous (undivided by any sutures) they can bear no struc- bercle, obliquely docked at the edge; below this series of 



tural affinity or homology with the frustra of Xylobius. tubercles, there are five or six other rows, diminishing grad- 



Another instance may be seen in Trachyjulus ceylanicus ually in size toward the base of the legs." Humbert further 



Pet. from Ceylon, specimens of which Professor Humbert states that, in this sculpturing of the segments, Trachyjulus 



has kindly given me an opportunity of examining, and which greatly resembles Glypftiulus granulatus Gerv. from Mauritius. 



are thus described by him (Essai sur les Myriapodes de Markings similar to the sutures dividing the frustra are 



Ceylan, pp. 43-46, pi. iii, figs. 18, 18a-18/i); "Each found in all lulids in the lines of growth on the lower borders 



segment is divided into three successive regions ; the front of the sides of the segments; but these invariably become 



one, formed by the articular portion (prozonite), fits into indistinct, and finally invisible at a short distance from the 



the preceding segment and is regular and smooth ; behind lower border of the segment, and, moreover, never traverse 



it is an annidar region marked by numerous projecting the segment in a straight line, but in a curve across the 



longitudinal lines ; finally the hinder part of the segment lower anterior angle, or in hues parallel to such a curve ; 



is prominent and furnished with strong longitudinal carina:, they are also closely approximate, while the division lines 



each formed of two- sharp spinous tubercles, placed one of the frustra are at comparatively wide intervals — alto- 



tehind the other and united at their base. These carina gether too wide to be mistaken for these lines of increment. 



