1920] 



Kew: Cretaceous and Cenozoic Echinoidea 



147 



situated immediately posterior to the center of the test. Petals of 

 the bivium slightly less than one-half the length of the anterior pair; 

 odd anterior one longest ; paired petals narrow and the anterior pair 

 bent slightly backward ; odd anterior petal much wider. Poriferous 

 areas wide. All petals situated in deep sulci, that of the odd anterior 

 one continuing through a deep notch in the ambitus to the peristome 

 on the inferior surface. Under side usually somewhat convex, and 

 produced posteriorly into a small knob. Peristome small, semicircular 

 in outline, and with a prominent posterior labrum. Periproct of 

 moderate size, suboval in outline, the greatest diameter being in a 

 vertical direction; placed high up on the posterior truncation of the 

 test. 



Related forms. — Among the California forms Hcmiaster cJiola- 

 mensis is most closely allied to H. alamedcvsis Kew, but may be dis- 

 tinguished by its very sliort posterior petals, deeper sulci in which 

 the petals are placed, narrower petals, and a much less prominent 

 knob on the lower posterior portion of the test. The Texan form, 

 H. iexari Clark, from the "Washita group of the Comanche series, 

 may be compared with this species, but H. cholamensis differs in 

 having a less rounded transverse profile, and in that the anterior petals 

 are narrower and those of the bivium are shorter. 



Geologic horizon. — Chico ( ?) formation. Upper Cretaceous. 



Locality.— Uoloiy^Q from center of Sec. 5, T. 24 S., R. 16 E., M. D. 

 B. and M., in southeast corner of Monterey County, California, Univ. 

 Calif, loc. 3141. 



HEMI ASTER OREGONENSIS Kew, n. sp. 

 Plate 41, figures 2a, 2b, 2c, M 



Cotypes.—'Noii. 11039 and 11040 Univ. Calif. Coll. Invert. Pal. 



Size relatively large. Measurements of tyj^e : anteroposterior di- 

 ameter 32 mm., transver.se diameter 32.5 mm., greatest lieight 14 mm. 

 Outline from above subcordate ; posterior extremity slightly truncated. 

 Test considerably depressed, with upper surface gently arched ; a low 

 ridge is present in the odd anterior interambulacral area which forms 

 the highest portion of the test. Apical system central or subcentral ; 

 petals large and well developed ; those of tlie bivium two-thirds the 

 length of the anterior pair, and somewhat narrower. Paired petals 

 subelliptical in outline ; outer rows of pores forming regular, curving 

 lines, while the inner rows extend in approximately parallel lines 



