in all growth stages of Olenellus (see plates 52-60). In the early stages of growth as in the examples shown in this plate, the eye lobe extends over a larger portion of the cranidial length than in the fully grown individuals such as that of plate 1. Other late meraspid exuviae are shown in (b) (xl.9) in an assemblage of one internal mold and two external impressions of approximately equal size. This and other similar assemblages from the same layers suggest some kind of size sorting in molting. P. gracilis is practically indistinguishable from P. paradoxissimus, except for the number of segments in adult individuals, twenty in the Bohemian (see plate 1), twenty-one in the Swedish Paradoxides. Specimens in (a) and (b) whitened with magnesium oxide. (RLS coll., donated by Dr. Petr Storch of the Geological Institute, Academy of Sciences of the Czech Republic, Prague.)
A well-preserved, diminutive example of Paradoxides gracilis (Boeck)(x4.5). M. Cambrian, Jinetz, Bohemia. (RLS coll.; courtesy of MCZ, now at FMNH.) Specimen whitened with magnesium oxide.
Beautifully preserved specimen of Paradoxides davidis davidis Salter, M. Cambrian, west side of Manuels River, Newfoundland (xl.3). This trilobite is first known from St. David's, Wales. A complete account of the evolutionary sequence that transpires from its fossil record in the Aval on Peninsula of Newfoundland is given in Appendix A of chapter 3. This particular example represents one of the earliest appearances of this trilobite at this locality. (External impression, specimen loaned through courtesy of Mark Utlaut.)
ACADOPARADOXIDES Snajdr, 1958. Acadoparadoxides sp., M. Cambrian, Sidi Abdallah ben el Hadj, Morocco (xO.65) (RLS coll.). These giant trilobites (up to 50 cm in length) are extracted commercially in staggering number and generally dubiously restored. The example shown, with eighteen thoracic segments, corresponds closely to Acadoparadoxides harlani (Green), as described by Walcott (1884), pi. IX., and may well represent the same trilobite. This would not be surprising since, as shown in figure 18, Maritime North America faced what was to become the Anti-Atlas Range in the Middle Cambrian.
HYDROCEPHALUS Barrande, 1846. Hydrocephalus hicksi (Salter), M. Cambrian, west side of Manuels River, Manuels, Newfoundland (x2.5). The libriginae are missing. Latex mold from external impression. (RLS id.)
ECCAPARADOXIDES Snajdr, 1958. Eccaparadoxides eteminicus (Matthew), M. Cambrian, E. bennetti beds, Kellygrews, Conception Bay, Newfoundland (xl.5). The cranidium is incomplete and the libriginae are missing. (RLS coll., id.)
Eccaparadoxides pusillus (Barrande), M. Cambrian Paradoxides davidis beds at Kellygrews, Conception Bay, Newfoundland (x3.6) (RLS coll., id.) The name of this long-eyed Paradoxidid is now regarded (Snajdr 1958) as synonymous with Paradoxides rugulosus Corda.
Eccaparadoxides oelandicus (Sjogren), M. Cambrian E. pinUS zone, Borgholm, Oland, Sweden (x6.7). Type specimen of late meraspid stage, described by Westergard (1936), pi. 2, fig. 4. (SMNH No. Ar 46244, photographed by the author at SMNH, through courtesy of Jan Bergstrom.)
Eccaparadoxides pinus (Holm), M. Cambrian, Borgholm, Oland, Sweden (x9). Type specimen of late meraspid stage, described by Westergard (1936), pi. V, fig. 7. (Photographed by the author at GSS, Uppsala, through courtesy of Christer Akerman.)
(Holm), M. Cambrian, Borgholm, Oland, Sweden (x2.0). Type specimen, described by Westergard (1936), pi. VIII, fig. lb. (Photographed by the author at GSS, through courtesy of Christer Akerman.)
Subfamily Xystndurmae Whitehouse, 1939
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