152 ECHINOIDEA. I. 



Accordingh' the species has been taken in considerable numbers and on niany localities, and 

 so it wonld be a remarkable faet, if it had not been taken before b}- any deep-sea Expedition. It 

 has also been taken, and siirely numbers of times; it has only been confounded with other species. 

 I am able to substantiate the following instances: From U. S. Fish Commission (Smithsonian Institu- 

 tion) our museum has received 4 specimens under the name of Echhitis riorvegicus\ the}' are typical 

 Ech. affinis. (< Albatross». 1884. 39° 35' N. L. 71° 24' W. L. 1043 fathoms.) In Challenger :-Echinoidea 

 Ech. iwrvcgiciis is mentioned from sts. 46 and 47 (eastern coast of North America, off Cape Cod) ; it is 

 also Ech. affinis. (On st. 46 it is taken together with Ech. Alexaudri, comp. p. 149). Accordingly there 

 can be no doubt that this species like Ech. Alexandri is found throughout the archibenthal zone of the 

 northern Atlantic, and possibly it is still wider distributed. In « Challenger ^-Echinoidea Echimis actittcs 

 is mentioned from st. 170, off the Kermadec Islands in the Pacific Ocean. After having examined the 

 specimen from this station in British Museum, I must positively assert that it is no Ech. acntiis\ on 

 the contrary it agrees with Ecli. affinis with regard to the tubercles of the ambulacral areas and the 

 pedicellariæ, and I have found no character, by which it might be distinguished from Ech. affinis. 

 Accordingly I must regard it as a rather stu'e faet that it is Ech. affi//is\ a more thorough examina- 

 tion will, however, be necessary in order to establish the faet definitively. — North of the ridges 

 between the Faroe Islands and Iceland, and between Iceland and Greenland it has not been foimd, 

 and at all events it is surely not found in the cold depth of the Norwegian Sea. 



The species Ech. Alcxaiiciri and affinis^ no doubt, are closely allied. As they are most fre- 

 quentl)' found together, it is an obvious thought that they might possibly be one species with a 

 marked difference of sex, although such a difference is otherwise very unusual in the Echinids. Of 

 this, however, there can be no question, as I have found both J and $ among specimens of affinis. 

 There can be no doubt that they are two well distinguished species. The form of the test, the 

 tubercles 011 the ambulacral areas, and especially the tridentate pedicellariæ yield excellent criterions 

 of them. But on the other hånd it may be very difficult or quite impossible to distinguish quite 

 young individuals of the two species, the more important specific characters being not yet typically 

 developed. From the < Ingolfs we have thus a rather great number of small specimens, which I am 

 not able with certainty to refer to one or the other of the two species. They are badly preserved, so 

 that no tridentate pedicellariæ are to be found. These pedicellariæ are otherwise early developed, and 

 give then all desirable certainty in the determination. The tridentate pedicellariæ seem not rarel\- to 

 be quite wanting in larger individuals, as may also be the case in Ech. Alcxaiiciri; the determination 

 of such specimens will, however, scarcely cause any difficulty, as especially the arrangement of the 

 tubercles in the ambulacral areas then will be a sufficient criterion. 



15. Echinus acutus Lanik. 



PI. I. Figs. 4, 7—8. PI. II. Figs. 1 — 2, 6, 8. PI. XV. Figs. 2, 14—16. PI. XVI. Figs. 2, 5, 10, 16, iS, 22. PI. XVIII. Figs. i, 5-7, 14, 24. 



PI. XIX. Figs. 32, 36. PI. XXI. Figs. 25—26. 



Principal synonyms: Eciiinns Flemingii Forb. 



— norvegictis Diib. Kor. 



— depressus G. O. Sars. 



