NIAGARA GROUP. 



189 



Fig. 1 a. An imperfect specimen of the head of this species, with a portion of the column at- 

 tached. 



Fig. 1 I. The structure of this species ; the upper portion of the figure including to the hase of 

 three of the arms, and the continuation of two of them being made out from the 

 exposed side of the specimen fig. 1 a. 



Fig. 1 c. A portion of one of the fingers enlarged, showing only one side with the tentacula 

 attached. 



Fig. 1 d. The base of one of the fingers enlarged, showing the commencement of the double 

 series of plates. The upper part of the figure connected by the dotted lines, shows 

 the union of the plates in the middle and upper part of the fingers, where they are 

 less deeply interlocked with each other. 



Fig. 1 e. A single scapular plate enlarged. 



Fig. 1 y. A portion of the column enlarged, showing the alternation of one thick plate with two 

 thinner ones, and, below this, of one thick and one thin one. 



Position and locality. In the shale of the Niagara group at Lockport. 



(^Collection of Col. Jewett.) 



583. 2. THYSANOCRINUS CANALICULATUS (n. sp.). 



Pl. XLir. Fig. 2o-d. 



Joints of the fingers alternating, and but slightly interlocking with each other on the back ; 

 tentacula adhering to the entire inner margin or face of the finger-joints ; first joint of tentacula 

 somewhat abruptly tapering from the finger-joints ; second and succeeding joints slender, with 

 prominent angles and a strong groove along the centre, slightly thickened at the joints ; sur- 

 face of the finger-joints simply granular, without any peculiar ornament. 



This species is only known from the fragments of several fingers with the tentacula attached, 

 one of which is shown in fig. 2 a. The character and proportion of the joints of the tentacula 

 furnish good characters for specific distinction. The first tentacular joints adhere to the entire 

 face of the finger-joints, and do not at all alternate with them. These joints, in the position in 

 •which the fragments lie, are two-thirds as long as the exposed width of the finger-joints, and 

 nearly twice their length. The deep groove and prominent smooth angles of the succeeding 

 tentacular joints contrast very strongly with the preceding and following species. 



Fig. 2 ffl. A fragment of one of the fingers, showing the tentacula on one side. 



Fig. 2 b. Two joints of the same enlarged, showing attachment of tentacula, form and proportion 



of joints, etc. 

 Fig. 2 c. The exterior of the finger enlarged, showing the union of the two series of joints. 

 Fig. 2 d. Vertical section enlarged, showing the position of the contracted tentacles. 



Position and locality. In the shale at Lockport. 



(Collection of Col. Jewitt.) 



