. Bulletin. Natural history; Natural history. 428 Illinois Natural History Survey Bulletin Vol. 33, An. 4 more than one of which may occur in Illinois, as discussed in the species account below. Cambarus tenebrosus Hay (Fig. 160) Cambarus bartoni tenebrosus Hay 1902 Cambarus bartoni laevis Faxon 1914 Description.—Rostrum broad, shal- lowly exca\ated, lacking median carina; margins slightly converging anteriorly, lacking terminal tubercles or spines; acumen short. Carapace dorsoventrally flattened, cervical spines absent (north- ern population) or present (southern population); suborbital margi
. Bulletin. Natural history; Natural history. 428 Illinois Natural History Survey Bulletin Vol. 33, An. 4 more than one of which may occur in Illinois, as discussed in the species account below. Cambarus tenebrosus Hay (Fig. 160) Cambarus bartoni tenebrosus Hay 1902 Cambarus bartoni laevis Faxon 1914 Description.—Rostrum broad, shal- lowly exca\ated, lacking median carina; margins slightly converging anteriorly, lacking terminal tubercles or spines; acumen short. Carapace dorsoventrally flattened, cervical spines absent (north- ern population) or present (southern population); suborbital margin gently angular. Areola moderately wide, nar- rowest part about 13-14 percent of length, with at least four punctations across. Chela large, heavily punctate; palm with one or two rows of tubercles on mesial surface. Form I gonopod terminates in two elements, both curved at an angle of more than 90° to the principal axis of the gonopod; a distally rounded sclerotized central projection, and a large tapering to broadly rounded mesial process. Dorsally rust red over- all, with abdomen slightly browner than carapace. In a discussion of the distribution and phylogeny of species of Cambarus, Hobbs (1969) depicted the range of C. (Erebicambarus) laevis as occurring mostly north of the Ohio River and that of the consubgeneric C. tenebrosus as being south of the Ohio River. Hobbs (1974b) separated the two species on the relative width of the areola ("at least 4 punctations across narrowest part" in C. tenebrosus; "no more than 3 punctations across narrowest part" in C. laevis) and the shape of the mesial process of the gonopod ("broadly rounded distally" in C. tenebrosus; "strongly tapered, often subacute" in C laex'is). Populations of the subgenus Erebi- cambarus occurring in southern Il- linois have been referred lo as C. bartoni brevis (Rietz 1912), C. bartoni laei'is (Brown 1955), C. laevis (Hobbs 1968,. Fig. 161.—Total distribution of
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