MIOCEJSTE ECHIXODERMATA. 189 



Geologic horizon. — Choptank formation, middle Miocene. 



Collections. — Maryland Geological Survey; Johns Hopkins University; U. S. National 

 Museum; Academy of Natural Sciences of Philadelphia. 



Scutella gabbi (Remond) Merriam. 

 Plate LXXXYIII, figure la-b. 



? 'Clypeastcr gabbi Remond, 1S63, California Acad. Sei. Proc, vol. 3, pp. 53, 54, no figure. See description on page 211 



of the present work. 

 tClypeastcr gabbi'Meek, 1S64, Smithsonian Misc. Coll., vol. 7 (1S3), p. 2. 



IClypeaster gabbi Gabb, 1S69, Geol. Survey California, Paleontology, vol. 2, pp. 36, 109, PI. XII, figs. G4, 64a. 

 IClypeaster gabbi Cooper, 1888, Cat. California fossils: State Mineralogist Seventh Rept., p. 271. 

 Scutella gabbi Merriam, 1899, California Acad. Sci. Proc, 3d ser., Geology, vol. 1, No. 5, p. 168, PL XXII, figs. 5, 5a. 

 Echinaracknius gabbi Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 703. 



Description. — The writer has been unable to obtain any specimens 1 of this form. The 

 description of Merriam will therefore be repeated verbatim: 



Test circular, much depressed, margin thin. Average specimens 25 to 30 mm. in diameter, largest specimens 

 ranging up to 40 and 45 mm. in diameter. 



Petals short, not extending more than two-thirds of the distance to the margin; excepting the anterior one, they are 

 nearly closed at the ends. Anterior petal wide open. Except in the anterior area the ambulacral plates suddenly 

 enlarge and the area rapidly widens beyond the ends of the petals. In these areas, pairs of small, round pores, diverging 

 strongly from the ends of the petals, may be present almost to the margins. In the anterior petal the plates do not 

 enlarge as noticeably toward the margin as in the others, neither do the more persistent pore pairs diverge as much. 



Apical shield with four genital pores, there being none at the end of the posterior interambulacral area. Anus 

 marginal to supramarginal ; in quite a number of specimens it is found to be entirely on the upper surface. Xo marked 

 difference is noticeable between the tubercles of the upper and lower surfaces. 



The ambulacral furrows of the actinal surface are not usualty well preserved and have been clearly seen on only a 

 few specimens; they divide dichotomously a little less than half way to the margin. 



Related forms. — The form described and figured by Merriam differs in several respects from 

 that originally described by Remond. Reinond's was subelevated, comparatively thick and 

 with margin rounded. Merriam's is much depressed, and with margin thin. The petals of 

 Remond's form were elongated and open at their extremities — those of Merriam are short and, 

 excepting the anterior one, are nearly closed at the ends. In Remond's form the ambulacral 

 furrows are straight, which led to his placing the form in the genus Clypeaster; in Merriam's 

 the furrows divide dichotomously a little less than half way to the margin, which indicates a 

 Scutella. These differences are too important to be ignored and raise the question whether 

 Merriam has described and figured identically the same form as Remond. The location of 

 Remond's type is unknown and he failed to give any figures ; but his other work is of too high an 

 order to justify any radical departure from his description, and his form is therefore placed in the 

 synonomy of the present species with an interrogation mark as indicative of the doubt that 

 exists in regard to the matter. It is not at all improbable that the investigator who obtains con- 

 siderable material from Remond's locality, San Pablo Bay, south of Mare Island, C'al., may dis- 

 cover a form more nearly corresponding to Remond's description than the one here described. 



Merriam's Scutella gahbi is most closely related to S. fairbanlsi, which, however, differs, 

 according to Pack, in ' ' attaining a greater size, in having a slightly undulating marginal outline, 

 in having deeper and better marked furrows on the actinal surface, and in having the anal pore 

 entirely upon the upper surface." 



Localities. — San Pablo Bay (Remond, Gabb, Merriam, Weaver) ; Walnut Creek (Gabb, 

 Weaver) ; and Martinez (Gabb), Gal. 



Geologic horizon. — San Pablo formation, upper Miocene. Merriam states that it occurs in 

 the lowest beds of the San Pablo formation. 



Collection. — University of California (19425). 



i Since this description was written the specimen figured was lent to the writer by Merriam. A study of this specimen strengthens the writer's 

 doubt as to its being the same form as that described by Remond. It has also made him inclined to regard Merriam's S. gabbi as very probably 

 the same as S. fairbanlsi Pack. 



30800°— 15 13 



