. Bulletins of American paleontology. Bulletin 339 of interporiferous zone at its greatest width. Petals clos- ing distally with poriferous zone of same petal almost in contact; petal III with 80 pore pairs (in both zones), petal IV with 84. and petal II with 82. Distinct am- bulacral groove extending ventrally from near margin to peristome. Peristome.— Siluaied slightly posterior to center with center of peristome located at distance from anterior margin equal to 54 %L. Size of opening uncertain be- cause of fracturing around peristome. Peripmet. —Located near posterior margin, opening wider
. Bulletins of American paleontology. Bulletin 339 of interporiferous zone at its greatest width. Petals clos- ing distally with poriferous zone of same petal almost in contact; petal III with 80 pore pairs (in both zones), petal IV with 84. and petal II with 82. Distinct am- bulacral groove extending ventrally from near margin to peristome. Peristome.— Siluaied slightly posterior to center with center of peristome located at distance from anterior margin equal to 54 %L. Size of opening uncertain be- cause of fracturing around peristome. Peripmet. —Located near posterior margin, opening wider than high with width = %L. height = %L. Sutures not clear enough to determine which plates enclose periproct. Diagnosis. —Species characterized by smooth dorsal surface with petals only slightly inflated, pore pairs widely separated from each other, resulting in fewer pore pairs in petals, ventral surface depressed only in vicinity of peristome. Type , NMB M9746. Comparison with other species. —This species is dis- tinguished from Clypeaster caudatus Jackson, 1922, which occurs lower in the Rio Cana section by its longer petals, wider poriferous zones, and in ha\ing the pore pairs in its petals more widely separated from each other in the same poriferous zones, resulting in fewer pore pairs in each petal. For example, a specimen of C. caudatus (NMB catalogue number unknown) with a petal II that is 39 mm long has 120 pore pairs, where- as the holotype of C maoadentroensis. having a slight- ly longer petal ( mm), has only 80 pore pairs. The greatest distance between two adjacent outer pores (measured along the length of the petal) near the mid- length (Text-fig. 4A) of petal III in the holotype of C maoadentroensis is mm, but is only mm in C caudatus (Text-fig. 4B) in petal III of a specimen of similar size. Furthermore, the peristome in C. maoad- entroensis is slightly posterior to the center, whereas it is central in C. caudatus. Fi
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