2/2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



Olenelliis nsaphoidcs (Emmons), Lindstrom, 1901, Kongl. Svenska Vet.- 

 Akad. Handl., Vol. 34. No. 8, pp. 12-18, text figs, i-io, p. 13. (Develop- 

 ment of cephalon discussed. Figs. 2 and 3 are copied from Walcott 

 [1886, pi. 17, figs, s and 6] ; figs. 5, 6, and 7 are copied from Ford, 

 [1877, pi. 4, figs. I, 2, and 3] ; fig. 10 is drawn from the cephalon of the 

 figure given by Ford [1877, pl- 4> fig- 5^ ; and figs. 8 and 9 are drawn 

 from the cephalons of the figures given by Ford [1881, figs, i and 2, 

 p. 251].) 



Olenellus (Mesonacis) asaphoides (Emmons), Clarke and Ruedemann, 

 1903, Bull. New York State Museum, No. 65, pp. 730-732. (A list of 

 the specimens (hypotypes) collected by Ford in the collection of the 

 New York State Museum.) 



Dorsal shield broad ovate, moderately convex. Cephalon large, 

 semicircular in outline, about two-fifths the length of the dorsal 

 shield ; genal angles extended into spines ; facial suture rudimentary 

 or in a condition of synthesis ; eyes elongate, crescentic, with ridges 

 uniting the palpebral lobes to the anterior lobe of the glabella in 

 the young, and in the adult a narrow furrow serves to cut oflf the 

 palpebral ridge from the glabella ; glabella elongate, increasing grad- 

 ually in width from the occipital furrow to the greatest width on the 

 anterior lobe ; anterior lobe large, convex, broader than the posterior 

 lobes, even in the earliest known stage of growth in which it is 

 defined [pi. 25, fig. 9] ; the three posterior lobes are subequal in 

 size, nearly transverse and separated by distinct, short lateral fur- 

 rows that are united by a shallow transverse furrow. In the young 

 the furrows are much deeper proportionally. Occipital ring strong 

 and well defined, w^hen not flattened in shale it has a small median 

 node. 



Thorax with eighteen segments ; body of pleurae nearly straight, 

 and with a broad furrow that extends out to the geniculation at the 

 base of the strong falcate extension of the pleurge. The five posterior 

 segments terminate on the line of the body of the pleurae in blunt, 

 rounded ends that curve backward at the posterior margin ; the 

 pleural furrows are narrow and shallow. The anterior thirteen seg- 

 ments have a small median node near the posterior margin of their 

 axial lobe, and each of the posterior five segments has a long, strong, 

 tapering spine that extends back over the pygidium. 



Pygidium small, transverse, and with only a trace of an anterior 

 segment. 



Surface finely gianulated, and with narrow, irregular raised ridges 

 that unite to form an irregular network over the glabella, axial, 

 and pleural lobes of the thorax ; on the cheeks and frontal limb of 

 the cephalon the ridges radiate from the base of the eyes and the 



