76 W. Baldwin — Fossil Myriopods from the Coal-measures. 



TRACEEATA (Air-breathers of the Coal Period). 



ARCHIPOLYPODA, Scudder. 



Fain. 2. Euphobeeid.e, Scudder. 



Genus Acantherpestes, Meek & "Worthen, Geol. Surv. Illinois, vol. iii 

 ( Paleontology), 1868, p. 556. 



1. Acantherpestes giganteus, Baldwin, sp. nov. (PL IV, Fig. 1.) 



This enormous specimen, which is to be presented to the Manchester 

 Museum, and of which a figure is given here (PI. IV, Fig. 1), was dis- 

 covered by the author at Sparth Bottoms last June, and is contained in 

 a large nodule weighing about 9 lb. 3 oz. Hoth sides of the nodule are 

 preserved, and expose the dorsal view of a Myriopod, having indications 

 of the tail and about twenty-five segments, measuring a total length of 

 195 mm. The telson (?) appears to possess a broad saddle which 

 terminates in the middle in a three-cornered area that is very 

 suggestive of Acantherpestes gigas (Fritsch). 



Each dorsal segment is divided transversely into two parts by a furrow 

 which extends to within a short distance of the lateral margin, dividing 

 the segment into two portions in the proportion of 2 to 5. The anterior 

 position is arched, whilst the posterior portion is curved to a height of 

 1*5 mm. The lateral borders of each segment are occupied by a broad 

 depressed margin prolonged backwards into a triangular area very 

 reminiscent of Arthropleura. The posterior portion of each segment 

 bears bosses and scars, representing three rows of spines on each side 

 of the body. The segments are all nearly of equal length, averaging 

 7"5 mm., their breadth varies from 18 to 44 mm., but the latter 

 measurement should actually be considerably modified on account of 

 the crushed state of the specimen. The change in breadth of the body 

 is very marked, and occurs in the last four or five segments (this is 

 probably caused by the loss of a part of the margin of these last 

 segments, and by their slight dislocation). 



The surface is apparently smooth, but when viewed with a strong 

 lens under a favourable light is found to be minutely granular. In 

 many places the surface integument has disappeared, revealing- 

 portions of the interior faces of the ventral plates, thereby exposing 

 large ovate oblong spiracles that run transversely through the body, 

 containing a deep groove with a thin laminate ridge along the middle ; 

 they are 2 - 75 mm. long and 075 mm. broad. On either side of the 

 medio- ventral line of the body, and almost attingent at their slightly 

 swollen bases, are the branchial cups, which appear as sunken pits, 

 triangular in form. A few pairs of ambulatory appendages can be 

 made out, two pairs being attached to each segment ; they are stout, 

 2 mm. broad, and probably attained 21 to 22 mm. in length. One 

 side of the specimen is very much flattened, and for about a length of 

 thirteen segments a dark stain is observed next to the lateral border, 

 and probably represents the soft portions of the animal which have 

 been squeezed out by pressure. 



This species differs from A. major in the shape of the segments, 

 and is easily recognized on account of its enormous size, hence the 

 trivial name. 



