Jan , 1914.] A Starfish found in Adams County. 223 



The aboral side of the rays and disc, as far as can be made out, 

 is rather less regular than the small portion of the aboral side of 

 P. dyeri figured. When one picks out the dorsolateral plates 

 with a lens however many of them are of the same quadrangular 

 type illustrated for P. dyeri. There is also a central depression 

 on each of these plates for the insertion of the spine as in P. dyeri. 

 It is possible that there are some shorter, slighter pieces which lay 

 between the rows of quadrangular or triangular plates. 



udambu I acral ^l cf'^ 



<n~ftYO- mar^o-i^i 



t ambul azYCxl 



plate. 



'^ "dCsc 



Fig. 2. Promo-palaeaster dyeri Meek (?) Natural size; ventral view 

 part of disc and arms. 



The crushing down of the arch of the aboral skeleton and the 

 mixing the broken spines from the surface in with the plates 

 makes it difficult to state precisely how many rows of dorsolateral 

 plates intervened between the supero-marginal plates and the 

 indistinct carinals which occupy the mid-dorsal line. The modem 

 starfish does not have as many dorsolateral plates as another 

 Richmond starfish, Palaeaster magnificus Miller, has. In this 

 respect my specimen seems more like the recent Asterias. 



The ambulacral plates seen from below are naturally partly 

 covered by adambulacral plates. There are, however, three 

 ambulacral plates at the end of the shorter arm which have lost 

 their adambulacrals. These are 5 m. m. long and a little more than 

 a millimeter wide. The locations of the pores through which the 

 tube feet passed are easily distinguishable. These ]3ores seem to 

 alternate so that each half of the ambulacral groove would present 

 two rows of tube feet. This alternation is only apparent as there is 

 but one tube foot in the opening between two consecutive ambula- 

 cral plates and one plate between two successive pores. The 

 device is correlated in the recent starfish, with a more rapid loco- 



