24- Beecher — New Permian Xiphosnran from Kansas. 



position and form with the earlier species. It is also possible 

 to detect an additional anterior pair, making the full number 

 of six altogether. 



jPrestioichia signata, sp. no v. (figure 1). 



A diagnosis of the species is necessarily quite incomplete, 

 owing to the fact that thus far only a portion of the internal 

 mold of a single cephalothorax has been discovered. It is 

 believed, however, that the characters preserved will readily 

 serve to identify the species, which is geologically quite 

 important. 



Cephalothorax large, depressed, convex, flattened on the dor- 

 sal side between the eyes, slightly arched in a longitudinal 

 direction. The glabellar region is marked by a subconical ele- 

 vation, angular along the median line, and terminating in front 

 by a small, round ocellar node, distant from the anterior margin 

 about one-sixth of the estimated length of the cephalothorax. 

 Extending from the posterior margin of the cephalothorax 

 are two low subangular ridges starting at points from the 

 median line equal to the basal diameter of the glabellar cone, 

 passing forward and curving slightly outward to the eyes, 

 thence turning a little toward the axis and merging into the 

 general contour before reaching the anterior end of the cone. 

 The space thus enclosed on each side is occupied by five low 

 rounded nodes, of which the posterior one is somewhat the larger 

 and obliquely pointed behind. Just at the apex of the cone, 

 and behind the ocellar node, is a pair of small transverse nodes, 

 thus making six on each side. The second and third of each 

 series are faintly delimited, while the fourth, fifth, and sixth are 

 very clearly shown. The glabellar axis also shows extremely 

 faint ambulations corresponding to the lateral lobes. Opposite 

 the third pair of lobes are the reniform or crescentic eyes, 

 which are large and prominent for the genus. Two minute 

 spots on each side of the small anterior median lobe, and distant 

 from each other about l'5 mm , indicate the ocelli. 



The surface of the specimen represents a mold of the inner 

 surface of the test, and is covered with a plexus of very slender 

 anastomosing vascular furrows and ridges, much like those in 

 the modern Limulus. 



The cephalothorax as preserved has a length of 45 mm . The 

 glabellar cone measures 33 mrn in length and 18 mm across at the 

 base. The outer edge of the eyes is about 20 mm distant from 

 the median line and measures fully 5 rom in anteroposterior 

 diameter. 



G-enal regions, abdomen, and telson unknown. 



Horizon and Lucality. — In the Fort Riley limestone of the 

 lower Permian, three miles west of Stockdale, Kansas. The 

 plastotype is in the Yale University Museum. 



Laboratory of Paleontology, Yale University Mnsemn, 

 New Haven, Connecticut, December 1, 1903. 



