262 



brachial spaces near edge of disc same as upper surface, but fad- 

 ing to nearly white near the mouth ; under arm-plates and mouth- 

 parts white, the former edged with reddish along their lateral 

 sides ; side arm-plates and arm-spines same as upper surface, but 

 lighter. 



Variations. A young one, with a disc of 2.7 millim., had 

 arms 7.6 millim. in length ; the color was mottled, pink and 

 white ; the disc was pretty closely covered with grains, or very 

 short spines, each bearing a crown of three little thorns ; the arm- 

 spines were rounded and conical, but not at all flattened. An- 

 other specimen had a disc of only 2.2 millim., and arms of 8.1 

 millim. ; this one had all the supplementary pieces of the upper 

 arm-plates covered with minute thorns. The smallest specimen 

 had a disc of 1.9 millim., and arms of 5.4 miUim. The disc gran- 

 ulation, arm-spines, mouth-papillae, and supplementary pieces of 

 the arm-plates, were all thorny. Arm-spines 5 ; mouth-papillae 

 2 ; lower arm-plates longer than broad, narrowest within, with a 

 reentering curve on the outer side and a notch on the inner ; 

 upper arm-plates longer than broad. 



This small species is distinguished from 0. Kennerlyi and 0. 

 aculeata by having the disc entirely covered with fine grains, 

 without naked plates. 



San Francisco, Cal. T. G. Gary. 



Museum of Comparative Zoology, Cambridge. 



Prof. Agassiz observed that among starfishes lately 

 received from Acapulco was a Pygorhynchus^ found liv- 

 ing there in abundance, — the genus being before known 

 only in the fossil state ; this would enable the structure 

 of this animal to be definitely made out. 



Dr. White called attention to a fine specimen of the 

 skull of a hippopotamus, recently purchased for the So- 

 ciety by subscriptions obtained by Dr. S. A. Green from 

 Messrs. James M. Barnard, J. N. Borland, William R. 

 Lawrence, A. A. Lawrence, and James Lawrence, to 

 whom the thanks of the Society were voted. 



