1920] 



Kew: Cretaceous mid Cenozoic Echinoidea 



71 



been collected from the type locality of the "eastern shore of San 

 Pablo Bay south of Mare Island, California, in soft sandstones of 

 Miocene age." The types used by Merriam were from the same 

 locality. 



Twitchell enumerates three sets of details in which the two de- 

 scriptions differ. These are as follows (quoting from Twitchell) : 

 "Remond'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 extrem- 

 ities — those of Merriam 's 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." The 

 terms used by both Remond and Merriam are for the most part rela- 

 tive, and their meaning is dependent upon the manner in which the 

 respective authors used them. For this reason the writer has con- 

 cluded that the first two sets should in this case be considered as of 

 little value in the determination of the similarity of the two forms. 

 In the third difference, whetlior the ambulacral furrows divide or not, 

 it was found, after examining a great number of specimens, that 

 straight, shallow, indistinct furrows do exist, but that in some cases 

 dichotomously bifurcating ambulacral lines are present. This, it is 

 believed, is sufficient evidence for placing this species in the genus 

 ScutcUa. Only one si)ecimen in the large collection available Avas 

 found which had bifurcating lines, though several forms showed the 

 ambulacral furrows. This last character is probably what Remond 

 saw and used as the basis of his determination of the genus. 



SCUTELLA GABBI var. TENUIS Kew 

 Plate 13, figures 4a, 4b 



Scutella gabbi var. tenuis Kew. Univ. Calif. Publ. Bull. Dept. Geol., vol. 8, 

 191.5, pp. 368-369, pi. 39, fig. 4. 

 Holotype. — No. 11005; figured specimen no. 11370, Univ. Calif. 

 Coll. Invert. Pal. 



This form is characterized by its extreme thinness. It is larger 

 than Scutella gabbi Remond. Average measurements: anteroposterior 

 diameter 33.5 mm., transverse diameter 34.5 mm., greatest thickness 

 5.8 mm. It is more strongly depressed ; its edge is much thinner, 



