OF THE TEST OF THE TEMNOPLEUEIDJi:. 345 



the pits (ati the cavities at the angles of the plates are properly- 

 called), or has satisfactorily explained the nature of a sutural 

 depression. 



I was impressed that the classification would be rendered 

 more satisfactory by a careful examination of the nature of the 

 cavities or pits at the angles of the plates, and of the so-called 

 sutural depressions or furrowings. 



II, Moiyliology of the Pits of Salmacis sulcata. 



In order to be exact, it is necessary to call the openings and 

 cavities at the angles of plates " pits,' ' and not pores. The suture 

 of two adjoining plates is really the whole junction of their edges ; 

 so that the superficial line denoting this on the surface of the test 

 should be called the margin of the suture. 



Specimens of Sahiacis sulcata, Agassiz, of many dimensions 

 and ages were examined in the firsb instance. 



On referring to the ' Eevision of the Echini ' by A. Agassiz 

 (p. 471), in reference to the genus it is noticed, " angular pores 

 at junction of plates." With regard to the specific diagnosis, it 

 is stated that the sutural pores are slightlj larger than those of 

 the species Salmacis iicolor, Agass. On turning to the descrip- 

 tion of that species, it will be found stated, " The pores at the 

 median junction are small, and the horizontal sutures of the 

 coronal plates slightly furrowed." In other words, the pits are 

 small and the margin of the suture is slightly furrowed. 



On examining the specimens before and after fracture, it was 

 evident that in Balmacis sulcata the pits at the angles of the 

 sutures, in the median interradial and ambulacral areas, occupied 

 what might have been the point of one plate and part of the line 

 between the edges of the adjoining plates, and that at the junction 

 of the tentaculiferous plates with the interradials there was a 

 vertical series of pits also interfering with the perfect shape of the 

 interradial plates. In fact, in some specimens the pits, as a whole, 

 seem to interfere considerably with the continuity of the test, 

 and would also seem to leave but little edge to some plates on 

 which sutural junction could take place. 



A Notice of the Nature of the Pits and Sutures of Salmacis 

 sulcata, Agass. — The pits of the test of Salmacis sulcata are in the 

 median lines of the ambulacral and interradial areas, and also at 

 the junction of the interradial plates with the tentaculiferous 



