. Bulletin of the Geological Society of America. Geology. DEVONIAN 283 forms the country rock, as in the Yukon as well as the larger confluent stream, the river valleys are narrow, with walls rising steeply from close to the water's edge. The smaller tributaries occupy A—shaped gorges. Alany small castellated peaks and pinnacles break the contour of the val- ley slope, giving an irregular topography along the watercourses. This irregularity is not carried back into the interstream .areas because of the general beveling to which the uplands have been subjected in a previous cycle. Fossils Avere
. Bulletin of the Geological Society of America. Geology. DEVONIAN 283 forms the country rock, as in the Yukon as well as the larger confluent stream, the river valleys are narrow, with walls rising steeply from close to the water's edge. The smaller tributaries occupy A—shaped gorges. Alany small castellated peaks and pinnacles break the contour of the val- ley slope, giving an irregular topography along the watercourses. This irregularity is not carried back into the interstream .areas because of the general beveling to which the uplands have been subjected in a previous cycle. Fossils Avere found at a number of localities in the limestones. At some exposures opposite the mouth of Woodchopper creek and about 1 mile farther up the Yukon the following fauna occurs in limestones inter- bedded with tuffs: Devonian Fossils ohtalnecl near Woodchopper^ CijatltopJti/lhim sp. Aiioplotlicca ? coiicava (Hall). Crinoid stems. Dalmaiiella sp. Stropheodonta cf. cah-iiii Miller. Spirifer sp. Camarotoechia, small sp. Renssela'ria ? sp. Atrypa reticularis Linu. Cypricardinia sp. Atrypa cf. flaiellata Goldf. Gonocardium sp. Schizophoria striatula (Schlotheim). Actinopteria near pcrstrialis Hall. Anihocwlia cf. umbonata (Com-ad). Pleurotomaria sp. Sigaretus ? n. sp. This is the same fauna and horizon as that occurring at the mouth of Salmontrout river on the Porcui^ine (see page 327). Atrypa cf. ffahcl- lata is one of the most abundant species in both faunas. The very pecu- liar gasteropod here referred doubtfully to Sigaretus and Stroplieodonta cf. calvini are also common to botli. About 2 miles below AVoodchopper creek the igneous beds which are there the predominant rocks are interrupted by a cliif of bluish gray Devonian limestone rising 200 feet al)ove the river. Fossils are very scarce here. The following species were obtained: Crinoid stems. Stropheodonta sp. Atrypa reticularis. Gonocardium sp. Camarotoechia sp. The base of the Devonian section is not exposed on the Yukon,
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