338 SYSTEMATIC PALEONTOLOGY 



" Thorax. A specimen from Valcour Island retains the last two seg- 

 ments of the thorax. They are narrow, extend horizontally, and on the 

 pleura are deeply grooved. The fourth segment is 5 mm. wide, .3 mm. 

 long and the axis is 1.6 mm. wide. The pygidium of the same specimen 

 is 1.25 mm. long, 4.3 mm. Avide, and the axis is 1.3 mm. wide at the 

 anterior end. 



"Pygidium. The pygidium is about three times as wide as long, 

 usually regularly rounded posteriorly, sometimes somewhat triangular. 

 Axis wide, prominent, extending to the posterior end of the pygidium. 

 The exfoliated axis shows seven to ten pairs of nodes very similar to those 

 noticed by Euedemann on specimens of Loncliodomas hastatus, from 

 Rysedorph Hill. The pleura show three or four pairs of rather indistinct 

 ribs. The margin is abruptly deflected all around." Eaymond, 1905. 



This little trilobite is one of the common fossils of the Middle Chazyan 

 (Crown Point) limestone of the Lake Champlain area, the types coming 

 from Highgate Springs, Vermont. 



Occurrence. STONES RIVER LIMESTONE (Middle division). Penn- 

 sylvania and Maryland. The old quarry at Chambersburg, Pennsylvania, 

 has afforded a number of cephala with the long spines preserved. 



Collections. Maryland Geological Survey, U. S. National Museum. 



Order OPISTHOPARIA 



Family CORYNEXOCHIDAE Angelin 



Genus DOLIGHOMETOPUS Angelin 



DOLICHOMETOPUS Sp. 



Plate XXVI, Figs. 1-9 



Description. More or less distorted cranida and pygidia of a probable 

 new species of this genus of trilobites occurs in the basal part of the 

 Elbrook limestone. Although the studies of this and allied species have 

 not progressed far enough to warrant description, illustrations are intro- 

 duced on pi. XXVI to show the varying aspect of such fossils under 

 pressure. 



