MUSEUM OF COMPARATIVE ZOOLOGY. 39 



23. Ptychoparia Attleborensis, sp. n. 



Plate II. Fig. 14. 



Head small, often minute; in the largest specimen, 4mm. long. The usual 

 size is about 2.6 mm. The glabella is oblong or slightly attenuate anteriorly. 

 The occipital groove is low or indistinct. The occipital ring extends beyond 

 the general posterior outline of the head, and apparently forms part of the 

 glabella before it. The glabella is sometimes intersected by faint lateral 

 grooves, of which there are three pairs, the anterior pair scarcely visible. 

 Oftener these grooves are obsolete, and the glabella may, in case the occipital 

 groove is very slight, appear as a continuous undivided body as far as the poste- 

 rior margin of the head. The glabella is always convex, and considerably ele- 

 vated above the general level of cheeks. There is in some specimens a very 

 slight trace of an ocular ridge, which runs from the anterior end of the gla- 

 bella laterally, and slightly posteriorly, joining a similar slight trace of the 

 palpebral lobes. The most marked feature of the fixed cheeks is the existence 

 of a depression along their postero-lateral outline. The anterior border is 

 proportionately very broad. About the character of the rim little can be said. 

 Near the lateral margin of the border, or rather near the facial suture, there are 

 sometimes two or three low tubercles visible. There is also in some specimens 

 a faint trace of a sufficient elevation of the border to indicate an incipient 

 marginal rim. A careful comparison of these specimens with published figures 

 of P. subcoronata, Hall and Whitfield, a specimen of similar size, shows numer- 

 ous differences, which are too marked to permit the Attleborough specimens 

 to be placed under the same species. 



Locality and position. — Station Xo. 2, North Attleborough, Mass., 

 Cambrian, 20 specimens. 



