ON THE FOSSIL PHYLLOPOD GENEEA, BIPELTIS AND 

 PROTOCARIS, OF THE FAMILY APODID.E. 



By Charles Schuchert. 



Assistant Curator, Dexmrtment of rale&ntolo()i/. 



The genus Dipeltis was establislied by Professor A. S. Packard in 

 1885 oil a specimen iii the collection of Mr. E. D. Lacoe, "not satisfac- 

 torily preserved, so that its exact relations are not readily determined 

 though it will be recognizable as a Cycluslike form." In the following 

 year the same author gave a more extended description, with a figure 

 of the type and a restoration of the dorsal side of the animal. Recently, 

 better preserved si)ecimens of 7>. ili2)lo(liscr(s have been found at Morris, 

 Illinois — one by Mr. J. C. Carr, and another, a nearly perfect individual, 

 by Mr. L. E. Daniels. All these fossils may be only sheddings, since 

 they are more or less cracked along the median ridge of the head shield 

 and the two large thoracic segments. An excellent specimen repre- 

 senting a new species, which preserves the cercopoda and probably 

 impressions of the anterior limbs, was found some years ago by Mr. 

 J. C. Carr. 



It is now certain that Dipeltls has no direct relationship with Cyclus, 

 nor is it a Xiphosuran, as supposed by Packard; also that the restora- 

 tion by the latter author is quite fnulty, and further that the family 

 Dipeltidic must be abandoned. The reason for these changes is that 

 DipeUis is closely related to Apus, as will be readily seen in Plate 

 LVIII, figs. 2-G. 



Genus DIPELTIS, Packard (emend). 



Generic characters. — Head shield subovate or subtriangular, nearly 

 smooth with two submargiual ocelli, and a pair of close-set eyes anterior 

 to the middle. Lateral angles acute in the adolescent stage, becoming 

 less so with maturity. Head shield not extended in one piece over the 

 abdomen, as in other Apodidie, but followed by two very large thoracic 

 segments, which at maturity have the lateral portions much extended 

 posteriorly, but less so in young specimens. Abdomen with from six to 

 nine segments. The telson, or anal segment (seventh in I), carri, tenth 

 in J), diplodiscus), is more or less wide, and bears laterally two slender 

 cercopoda, or cirri. 



Proceedings U. S. National Museum, Vol. XIX— No. 1117. 



Qii. 



