Verrilly Notes on liadiata. 816 



ble to the unaided eye, nearer to the center than the genital pores. 

 Spines nniformly crowded above and beneath, short and slender, the 

 larger ones of the upper surface mostly with slightly enlarged tips. 

 Color, in alcohol, dark ash-brown. 



This species is allied to S. prostratus (Kav. sp.) of the West Indies, 

 but has a thinner margin, broader ambulacra, a larger rosette, and a 

 thinner test. 



PygorhynchuS PacificUS (Ag. MS.) A. Agassiz, Bulletin M. C. Z., p. 27. 



We have received from the Museum of Comparative Zoology, two 

 specimens of this very interesting species, collected by Mr. A. Agassiz 

 at Acapulco ; and young specimens, from the Smithsonian Institution, 

 collected at Cape St. Lucas by J. Xantus. 



One specimen is rs inches long ; 1*4 broad; "9 high; from center 

 to anterior margin 1 ; to posterior margin 1"22; to anal orifice "9; to 

 end of anterior ambulacral ray 'lb ; to end of anterior-lateral '1 ; to 

 end of posterior-lateral "8; width of ambulacral rays "18; the median 

 area "l ; width of actinal opening '2; length '12. Another specimen 

 is 1 "9 long ; 1 '6 wide ; 1 high. 



Test thin, concave beneath, the sides most prominent opposite the 

 mouth ; above regularly arched except at the anal region ; marginal 

 outline oblong, the ends obtusely rounded, the posterior portion 

 broadest. Anal area transversely oval, situated in a depression above 

 the margin. Ambulacral rays nearly equal in width, the posterior 

 ones longest; the anterior poriferous zones in the anterior-lateral 

 ambulacra and the posterior zone in the posterior ones, shorter and 

 narrower than the others. From the ends of the ambulacral rays two 

 single rows of poi'es may be traced around to the mouth, in most of 

 the ambulacra. The actinnl opening is wider than long, with five 

 angles alternating with prominent lobes. One of the angles is on the 

 anterior side, with a lobe opposite. A rosette of pores surrounds the 

 mouth, each ray having two short rows of double pores and two rows 

 of few, larger, single pores within them, and in the center another 

 very short row of double pores, the pair next the mouth larger. The 

 " naked space " beneath is broadest anteriorly, enclosing the mouth, 

 and narrowing posteriorly. In life it is covered by minute spines. 

 The spines of the upper surface are short and delicate, crowded ; on 

 the sides of the lower surface they are longer and larger, tapering, 

 sharp at the ends, longitudinally fluted. Tubercles of the upper side 

 small and regular ; on the lower surface they are larger and sunken 

 on the lateral parts ; very small and unequal on the median area. 

 Genital openings four, near the center. Color, Avhen dried, brownish 

 yellow. In alcohol, darker yellowish brown. 



