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caused the appearances which he believed to be bubble marks, 

 said that he felt confident specimens in the possession of Mr. 

 Teschemacher would convince him that such could not have 

 been their origin. 



Mr. Ayres remarked, that his researches among the Echi- 

 nodermata of our coast had shown the existence of a singu- 

 lar law of distribution. 



Of the Holothuridse very few species are identical with Euro- 

 pean forms or even closely allied to them. Among the Ophiu- 

 ridse a greater resemblance prevails ; a larger proportion of the 

 species inhabiting both shores of the Atlantic, and those which 

 are confined to our coast more nearly representing the types of 

 Europe ; while among the true Star Fishes all the species yet 

 discovered are either identical with those of Northern Europe or 

 intimately allied to them. 



Mr. Ayres also gave an account of the structure of the 

 Ophiuridae, and presented a description and drawings of a 

 new species belonging to the genus Ophiolej)is, 



O. tenuis Ayres. This is a small and delicate species, the 

 disc in the largest specimens being not more than a fifth of an 

 inch in diameter ; the breadth of the disc is contained nearly four 

 times in the length of the rays. The lateral ray-plates bear 

 each two to four slender spines not equalling the breadth of the 

 ray. The superior and inferior ray-plates are broadly-ovate, 

 somewhat angular laterally. 



The superior surface of the disc is covered with small, smooth 

 plates, the origin of each ray being marked by a pair of larger, 

 oval plates, having their narrow extremity outward, and touch- 

 ing each other through their whole length. 



The plates forming the angles of the mouth have but a small 

 number of teeth or divisions, generally from five to seven. The 

 inter-brachial plates are similar in form to the inferior ray-plates, 

 but smaller. 



This species inhabits Boston Harbor, being frequently found 

 creeping over the stones, shells, &c. brought up in the dredge 

 from the depth of three to six fathoms. It is of a dark grayish 



