CLYPEASTER LYTOPETALUS. 33 



on individual \-ariants. In regard to retaining the name japonicus instead of 

 clypcus. which precedes it on the page, the choice is determined by the fact that 

 clypeus is based on a single atypical specimen while japonicus is based on a 

 series of specimens. Moreover the name japonicus is to be preferred, as more 

 appropriate. As the International Code simply recommends the adoption of 

 "page precedence" "other things being equal," I have thought best to retain 

 japonicus, as other things are not equal. 



In conclusion, it may be mentioned that the primary spines are smooth 

 and the miliaries are club shaped. Pedicellariae are abundant but no triphyllous 

 were noted. Alany tridentates are very small, the valves less than .15 mm. long, 

 but they range up to 1.10 mm. ; the valves show an equal diversity in slenderness, 

 the length of the heads ranging from 1.5 to 2.25 times its thickness at base. 

 The ophicephalous pedicellariae occur chiefly near the ambitus and have heads 

 .30 mm. long, more or less. 



Clypeaster lytopetalus.' 



A. Agassiz and Clark. 1007. Bull. M. C. Z.. 50, p. 24'^. 



Plates 124, figs. 1, 2; 138, figs. 1-3. 



Length, 33 mm.; breadth, 26 mm.; height, 10 mm.; mouth sunken 3.5 mm. 

 below sides of test. Test evenly convex, sloping uniformly from ambitus to 

 apex. Tuberculation of test rather coarse, about a hundred primary tubercles 

 to a sq. cm. of surface; these tubercles are relatively large with sunken areolae; 

 ridges between pore-pairs of unpaired petal, with only one primary tubercle 

 or none; miliary tubercles numerous but very small and often only faintly 

 indicated. ^ladreporite pentagonal, 1.5 mm. across; ocular plates and pores 

 distinct but genital pores wanting. Unpaired petal, with thirty-six pairs of 

 pores on each side, 10 mm. long, 5 mm. wide at middle and 6 mm. wide, half way 

 between middle and tip; median area 3 and 4 mm. wide at same two points 

 respectively; hence poriferous areas are about 1 mm. across where widest; petal 

 open by fully 2.5 mm. Anterior petals only 8 mm. long, but 6 mm. wide, closed 

 at tip. Posterior petals 9.5 mm. long and (1 mm. wide, slightly open at tip. 

 Periproct very near margin about 2 mm. across, covered with 25-30 plates, 

 most of which bare one miliary spine (rarely two). 



Primary spines, smooth, slender; on aboral surface hardly more than a 



' \vTo from Xiiu = to open -|- TriraKov = [x'tal. in rcfcrcnrp to tlip open, unpaired petal. 



