. Bulletins of American paleontology. 14 Bulletin 313 of comparison, because it appears to reduce the bias inherent in comparing samples of different sizes (for discussion of the various binary coefficients which might have been employed, and their attributes, see Cheetham and Hazel, 1969). The use of the genus as a standard in this and following comparisons for cor- relative purposes follows the rationale of Grant and Cooper (1973, p. 573). The results of the above com- parison appear in Table 2. This shows that although all similarity levels are low, the highest level of simi- larity lies be
. Bulletins of American paleontology. 14 Bulletin 313 of comparison, because it appears to reduce the bias inherent in comparing samples of different sizes (for discussion of the various binary coefficients which might have been employed, and their attributes, see Cheetham and Hazel, 1969). The use of the genus as a standard in this and following comparisons for cor- relative purposes follows the rationale of Grant and Cooper (1973, p. 573). The results of the above com- parison appear in Table 2. This shows that although all similarity levels are low, the highest level of simi- larity lies between the Palmarito Formation and the Road Canyon and Cathedral Mountain Formations of West Texas. In Table 1, one can readily appreciate the great dif- ference in brachiopod generic composition between Locality 6 and all other Palmarito Formation localities. This suggested the desirability of determining how many distinctive generic assemblages of brachiopods existed within the Palmarito Formation. To do this I calculated the similarity in generic composition of bra- chiopod assemblages at sampled localities within the Palmarito, and then systematically compared these groups with brachiopod assemblages from finer strati- graphic subdivisions in the better-known West Texas region. Again using the Otsuka Coefficient, the genera recovered at each locality were compared to those from every other locality, and the results were plotted as a similarity matrix (Text-fig. 2). While this matrix contains all the information needed to determine the degree of similarity among the localities, it lacks visual Table I.—Occurrences of brachiopod genera in Palmarito For- mation fossil assemblages, x = presence; - = Localities Genera 1 2 3 4 5 6 7 8 10 11 13 Acosarina _ _ _ _ _ _ y - - _ _ Anaplychiiis - - - - - X - - - - - Anemoniiria X - - - - - - - X X - Aneuthelasma - - - - - X - - - - - Chonetineles - - - X - - - X - - X Cteiothvridina - - X - - - - - - - - Collemataria - - - -
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