DISCOVERY OF SONORASPIS IN SOUTHERN CALIFORNIA
Genus Sonoraspis was erected b y the senior writer (Stoyanow, 1952, p. 50, PL 14, figs. 1-6) for the Midd le Cambr i an tri lobites f r o m Sonora, Mexico, which differ f rom Anoria Walco t t (1924, p . 54; 1925, p . 67) and Glossopleura Poulsen (1927, p . 268), under which generic names they h a d been originally listed (Stoyanow, 1942, p . 1263-1264), in hav ing eight instead of seven thoracic segments and in possessing mixed character is t ics of those two genera. T h e discovery of Cambr i an tri lobites in Sonora led McICee (1947, p. 282) to pos tu la te an early Middle C a m b r i a n seaway f rom t h e Grand Canyon area to Sonora across sou th western Arizona. Th i s view was based chiefly on the presence of Glossopleura in H a r q u a h a l a M o u n t a i n s south of the G r a n d Canyon . T h e above in te rpre ta t ion was opposed b y t he senior wri ter (Stoyanow, 1948, p. 323-324) who pointed o u t the absence of C a m b r i a n s t r a t a between the two regions, and especially the fac t t h a t in C a m b r i a n t ime sou thwes te rn Arizona was occupied by the P recambr i an massive, Al tar Head land (Stoyanow, 1942, p . 1264) of Maza t za l L a n d (Stoyanow, 1936, p . 462; cf. Cooper and Arellano, 1946, p . 608), which p robab ly extended sou thward in to Sonora. A westward Paleozoic por t a l in the Sonora basin was suggested. A tri lobite of the Anoria-Glossopleura g roup b u t with eight thoracic segments , collected f rom the Middle Cambr i an s t r a t a in Bris tol Moun ta ins , sou thern California, was described as Balhyuriscus howelli var . lodensis b y Clark (1921, p. 6) b u t was no t f igured. L a t e r Resser (1928, p . 10, PL 3, fig. 9) i l lustrated Clark ' s t ype advancing i t to the s t a tu s of species, Dolichometopus? lodensis (Clark) , and also ment ioned eight thoracic segments . H o w ever, in a more recent pape r Resser (1935, p . 29, 34) placed this species, as Glossopleura lodensis (Clark) , wi th o ther species possessing only seven thoracic segments, as also did M a s o n (1935, p . 109, PL 15, fig. 11) while describing, as Anoria lodensis, a plesiotype of Clark ' s species collected in Marb le M o u n tains. Like Anoria, Clark 's species has a macropleural fifth thoracic segment . T h e illust ra t ions of Resser and Mason do not allow the figuring of the number of thoracic segments (eight as by Clark, or seven as by Resser and Mason) in either of two types wi th any degree of assurance. Clark 's holotype was no t available a t the t ime of this writing, b u t Mason ' s plesiotype, preserved in the Los Angeles M u s e u m , has been examined by the writers th rough the kindness of D r . G. P . Kanakoff . I t has seven thoracic segments with the fifth segment macropleural as in Anoria. Since the thoracic axis is completely destroyed in this specimen, it is impossible to establish the presence or absence of the axial tuberculat ion. T h e possible presence of Sonoraspis in southern California, as suggested by Clark 's ment ion of eight thoracic segments, s t imulated a more detailed research in the Middle Cambr ian s t r a t a of California. Th rough indefatigable and sys temat ic field studies the junior writer eventual ly located Sonoraspis in Marb le M o u n t a i n s abou t 50 feet below the base of Bonanza King format ion. Like 5 . torresi and 5 . gomezi of Sonora, it has, besides the presence of eight thoracic segments of the generic diagnosis, and like those two species, certain mixed character is t ics of Anoria and Glossopleura. Sonoraspis califomica, sp. nov., has tubercles on the anterior thoracic segments and the course of the facial sutures as in Anoria, b u t like Glossopleura i t lacks the macropleural enla rgement of the fifth thoracic segment. If Clark 's species f rom Bristol Moun ta ins has eight segments in the thorax, it is distinguished by the presence of the la t ter characteristic. T h e diagnostic description of the new species is presented below.