1873.] WRIGHT — SILURIAN STARFISH. 421 



ornament on the hinder margin is the same in both. On the whole 

 this Liassic dogfish corresponds most nearly with the Cestracion of the 

 present day in its dentition and the arrangement of the dorsal fins ; 

 but in the proportion of the head to the trunk, and in the elon- 

 gated and slender contour of the latter, it has more resemblance to 

 Acanihias. 



Discussion. 



Dr. Gunther observed that the families of Sharks were most 

 sharply characterized; and that of the Spinacidas especially was a very 

 natural group. He did not, in the instance cited, doubt the absence 

 of a separate anal fin, which was one of the characteristics of the 

 Spinacidse. He drew attention to the fact that the spined sharks 

 showed several singular peculiarities with regard to their geographical 

 distribution. Some belonged to the deep sea, and were found at a 

 depth of 800 fathoms, while others were even more truly pelagie 

 forms, and never approached the shore. Some were found both in 

 the northern and southern hemispheres so similar that specimens 

 from the British seas and from the Straits of Magellan and Australia 

 could not be distinguished. The geographical distribution was of 

 great importance in considering the palasontological aspect of such 

 a case. 



4. On a new Genus of Silurian AsTERiADiE. 

 By Thomas Wright, M.D., F.R.S.E., F.G.S. 



[Abstract.] 



The specimen described showed the outline of a small Starfish, 

 with a large disk and short rays, in a slab of "Wenlock Limestone 

 from Dudley. The outline of the ten rays was described as marked 

 out by the border of small triangular spines, the other plates of the 

 disk and rays being absent. Each ray was terminated by a stem- 

 like multiarticulate process as long as the ray, from towards the 

 extremity of which spring slender lateral processes, giving it a tufted 

 appearance. This Starfish, which is in the collection of Dr. Grind- 

 rod, F.G.S., is named by the author Trichotaster plwmiformis. 



Discussion. 



Mr. H. "Woodward was somewhat doubtful as to the affinities of 

 the specimen, the preservation of which appeared to him hardly 

 sufficient for its specific determination, though of all men Dr. "Wright 

 was the best qualified for such a task. 



