. Second contribution to the studies on the Cambrian faunas of North America [microform]. Paleontology; Arthropoda, Fossil; Arthropoda, Fossil; Paléontologie; Arthropodes fossiles; Arthropodes fossiles. I ' ' ' M \h 'â i't'' tn;:'. II 176 CAMBRIAN FAUNAS OF NORTH AMERICA. fn"r I,. 30. or , and even more so in the cheek, fig'. \c of pi. xviii, if it cut the posterior margin at the angle x, as it does in all known cases in the smaller specimens, tis. 1/t and 1?'. Coiuparin^^ this with tlie direc- tion of the stages of growth shown on figs. \e and \g, wiiere anotlter gene
. Second contribution to the studies on the Cambrian faunas of North America [microform]. Paleontology; Arthropoda, Fossil; Arthropoda, Fossil; Paléontologie; Arthropodes fossiles; Arthropodes fossiles. I ' ' ' M \h 'â i't'' tn;:'. II 176 CAMBRIAN FAUNAS OF NORTH AMERICA. fn"r I,. 30. or , and even more so in the cheek, fig'. \c of pi. xviii, if it cut the posterior margin at the angle x, as it does in all known cases in the smaller specimens, tis. 1/t and 1?'. Coiuparin^^ this with tlie direc- tion of the stages of growth shown on figs. \e and \g, wiiere anotlter generic gronp is suggested l)y its Paradoxides-like course, the contrast is very striking. It is stated on p. 34, Monographs United States Geological Survey, vol. viii, that in adult specimens of O. Gilherti and 0. Vernionfana the course of the facial suture is almost directly backward from the eye to the margin. This statement was based on the published figures of the two species. I now have before me the type specimens of (). Gilherti, and I fail to find a trace of the facial suture sliowing on any one of ihem, and their course is not mentioned by either ^Ir. Meek or Di. Wlii't', tlic artist evidently having indicatetl in the drawings his personal views of where they should be placed. In well-preserved speciuiens of O. Thouipsoni the suture back of tlie eye extends outward to the pleural angle, as in O. Gilharti. ?[ode of (lerelopmtiif.âThe iiorniid development of a trilobite from tlic earliest embryonic condition with which wc are acquainted to the adult form is marked by the disai>])earance of the embryonic characters, one by one, as the individual increases in size and assunu\s unnv and juore the features of the fully develoi»ed animal, all of which usually takes place, except in size and surface ornamentations, when it is quite small. Tlie retaining of au embryonic feature after the imlividual has passed in size, or in any other character, the stage at which it usua
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