ECHIXOIDEA. II. 



63 



area of the Atlantic 1— its occurrence in tlie Bay of P>i.sca\- (Norman, op. cit.) niu.st likewise be re- 

 garded as dotibtful, the statement evidently being; made without a close examination of the speci- 

 mens — ), and I doubt that it will be found there. Pourtalrsin /efrcysi is the onl\- deep sea Echi- 

 noid known from the cold area; it is only known from there, and it will jirobablv turn out to inhabit 

 the cold area alone, as has been proved for mo.st of the animal forms of that rej^ion. I-'roni lliis con.sid- 

 eration Grieo; (op. cit.) has already doubted the correctness of the identification of tlie specimens 

 from the American coast recorded by Profes.sor Verrill under the name of Poiirtalesia Jcffrcysi, and 

 the doubt was cpiite justified. 



22. Pourtalesia Wandeli Mrtsn. 



PI. V. Figs. 1—7, II — 12. PI. VIII. Fig.';, i— j, 7. PI. XI. Figs, i, 13—14, iS— 20, 23, 34—37, 40-41. 



Th. Mortens en: Some new species of Echinoidea. Vid. Medd. Naturli. I'"oren. Kobeuhavn 

 1905. p. 242. 



The shape of the test is rather elongated, more .slender than in P. Jrff'rcysi. The front end is 

 almost vertical; on the abactiual .side the test rises genth- towards the middle, where the greatest 

 height is found, and then slopes gradually towards the posterior end. An abactiual keel is hardlv 

 indicated in larger specimens, whereas it may be more distinct in smaller ones. The test is not pro- 

 duced over the periproct; in side view the outline of the abactiual side is thus seen to continue to 

 the posterior end of the short anal rostrum scarceh- without any sinuatiou o\-er the periproct, a \-er\- 

 conspicuous difference between the species and P. Jrffreysi, as is seen on comparing the figures 11 and 

 13, 18, 23 of PI. V, representing side views of the tests of these two species. — In younger specimens 

 the outline in profil of the posterior end is somewhat different (PI. \'. Figs. 5, 12) in accordance with 

 the more developed abactiual keel, the periproctal siuuation being considerabh' more distinct. The 

 sides of the test are almost parallel, the width augmenting only very little towards the posterior half, 

 the greatest width being found a little past the middle; from there it"rapidl\- narrows towards the 

 posterior end. The actinal side is almost flat — a conspicuous difference from P. Jrffreysi, as is seen on 

 comparing the figures 11,12 and 13,18. PI. V. Among smaller specimens of the two species this differ- 

 ence is, however, not so great, I^. frffrcysi being flatter on the actinal side when younger. The 

 sternum and episternum form a rather distinct actinal keel, which continues along the under side of 

 the anal snouL The actinal invagination is somewhat longer than in P. Jrffreysi; the number of plates 

 in the odd ambulacrum is, however, the same as in Jrffreysi. 12 — 13. The form of the peristome as in 

 Jeffrcysi. — The test seems to me a little more fragile than in Jrffreysi. 



Regarding the structure of the test this species agrees in the main features with P. Jrffreysi. 

 The labrum is generally not seen from without, ma>', howe\'er, l^e found as a small plate between the 

 ambulacrals I. a. i and V. b. i, which are distinctl}- developed: eight sim]ile pores are found at the 

 posterior edge of the invagination (Pi. \TII. Figs. 1,3); none of the inner ambidacral plates have two 

 pores. If the tube-feet are developed on all the plates I dare not assert, as it is rather difficult to dis- 

 cern them among the small spines in this place, both spines, tube-feet and skin being covered by 

 dark violet pigment; also the pores may be very difficult to discern, as in l\ Jrffreysi. A small 

 plate ma\' be found between the ambulacrals I and II on one side and between IV and \' on the 



