MARYLAND GEOLOGICAL SURVEY 347 



without traces of ribs. Border narrow, concave; doublure narrow, con- 

 vex. Hypostoma quadrangular, widest in front, central portion convex, 

 with a furrow and narrow border around the sides and posterior end. 

 Surface of all parts, including the hypostoma, covered with imbricating 

 striae. 



"One pygidium is 9.5 mm. long and 18 mm. wide; a larger one is 

 14 mm. long and 28 mm. wide." Eaymond, 1910. 



As noted by Raymond this species much resembles Asaphus gyracanthus, 

 but its cephalon is shorter and wider, the eyes are farther apart and the 

 axial lobe of the pygidium is much more prominent. 



Occurrence. BEEKMANTOWN LIMESTONE (Stonehenge member). 

 Hagerstown, Maryland and Bellefonte, Pennsylvania. 



Collection. U. S. National Museum. 



Genus SYMPHYSURUS Goldfuss 



SYMPHYSURUS CONVEXUS (Cleland) 



Plate XXXII, Figs. 16-18 



Asaphus convexus ? Cleland, 1900, Bull. Amer. Pal., vol. iii, p. 128 (256), 



pi. xvi, fig. 4. 



Bathyurus sp. Cleland, 1900, Idem., pi. xvi, fig. 9. 

 Illaenurus columbiana Weller, 1903, Pal. New Jersey, vol. iii, p. 133, pi. v, 



figs. 1-4. 



Bathyurus f levis Cleland, 1903, Bull. Amer. Pal., vol. iv, p. 36, pi. ii, figs. 1, 2. 

 Symphysurus convexus Raymond, 1910, Ann. Carnegie Mus., vol. vii, No. 1, 



p. 42, pi. xiv, figs. 14-16. 



Description-. Entire cephalon unknown ; glabella oblong, convex, with 

 the eyes located halfway between the front and back. A small median 

 tubercle present, below the eyes. Thorax unknown, but its axial lobe is 

 probably narrow. Pygidium semicircular with a distinct axial lobe. 

 Several indistinct annulations are present. 



The types of both this species and its synonym Bathyurus ? levis 

 Cleland were obtained in the Tribes Hill limestone at Fort Hunter, New 

 York. The species was identified by Weller in the Canadian portion of 

 the Kittatinny limestone at Columbia, New Jersey, and under the belief 

 that the species belonged to Illaenurus, the new name Illaenurus colum- 

 biana was proposed, the name Illaenurus convexus being preoccupied. 



