56 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. 



have been united by Lahille in his monograph on these forms into one 

 species, for which he creates the new genus Iheringia. This generic name, 

 being preoccupied by Keyserling in 1891, has been changed by Berg 

 (1898, p. 1 6) into Ilieringiella (non Iheringella Pilsbry, 1893), an d again 

 into Ihcringiana (Berg, 1898, p. 41), and finally Lahille himself (1899, P- 

 5 of separate copy) has changed it into Iheringina. 



After a careful study of our rich material I am prepared to accept Lahille's 

 view as to the identity of these supposed two species, as well as his views 

 on the respective value of the genera Echinarachnius and Scutella, but I do 

 not think that the Patagonian fossil ought to be placed in a separate genus 

 ( Ilio'ingia = Iheringiana Berg) ; I prefer to leave it with the genus Scute/la. 



In discussing the differences of Echinaracknius and Scutella, Lahille 

 has overlooked the fact that A. Agassiz (1872, p. 315) has given a charac- 

 ter, by which the subgenus Echinarachnius may be distinguished from the 

 true Scutella, viz., the arrangement of the pillars in the interior of the test. 

 In Echinaracknius (as well as in Dendraster 2cs\& Scaphec limits] the pillars 

 are more or less concentric with the edge of the test, while in Scutella they 

 recall more the stellate arrangement of Mellita. This is said to be the 

 only ground on which Echinarachnius might be separated from Scntella. 

 I have tried to verify this character, but did not meet with much success. 

 Failing to find any good figures representing the interior of the test of 

 Scutella, I have compared that of Mellita as given by Agassiz (1872, pi. 

 I2a, f. 14) with those of the interior of Echinarachimis (Agassiz, pi. I3a 

 and i id, f. 45) and of Iheringia (Lahille, 1898, pi. 2, f. 11, 12), and do 

 not find any essential differences, except that in Mellita this system of 

 pillars is more complex, but it shows nevertheless distinctly a concentric 

 arrangement near the edge (especially fig. 4 on pi. i2a of Agassiz). As 

 to Scutella, I have chiefly compared the account and figures of Scut, sub- 

 rotunda given by Quenstedt (1875, p. 544, pi. 83, f. 2, 4), and also do not 

 find any differences from Echinarachnius; indeed, the different sections 

 given by Quenstedt in fig. 4 render it beyond doubt that the concentric 

 arrangement of the pillars in Scutella agrees with that of Echinarachnitis. 



Thus it appears that even this character does not permit a separation of 

 Echinarachnius from Scutella, both genera (or subgenera) being practically 

 identical ; all the characters given as distinctive (outline, ambulacral fur- 

 rows of lower side, position of anus, shape of ambulacral petals) are only 

 of specific value. 



