ECHINOIDEA. II. 121 



uns ont trois, les autres qiiatre et d'antres deux pores ; but in the first place it is, as remarked by 

 Liitken (Bidr. til Kundsk. oui Ech. p. 115), uncertain which species is really meant, and in the second 

 place there is no certainty at all that these specimens have realh- all been of the same species. — 

 For the /ra^i/is-growp no case is known of the occurrence of more or fewer than three genital pores. 

 It is thus beyond doubt that the number of genital pores is an important and constant character, 

 distinguishing the two groujis of species. — This feature has been shown by Tornquist (Op. cit.) to 

 be of importance from a palæontological point of view. The oldest (Cretaceous) Sch'zas^er-s-pecies 

 have all 4 pores; from these the develoijment goes in two separate directions: to the symmetricai 

 2-pored and the asymmetricai 3-pored species; the latter form is not known before the Miocene. The 

 recent Sch. gibbcrnlns and Savignyi thus seem to be comparatively primitive forms. Pomel (Op. cit. 

 p. 36) raakes Sch. gibberitlns the type of a separate genus, Paraster, which may perhaps be correct; as 

 long as the pedicellariæ of this species (and Savignyi) are unknown, it seems, however, better to leave 

 the question undecided; but it is worth noticing that these two species differ from the canaliferus- 

 group also in the lower shape of the test, besides in having four genital pores. 



Another character uniting the species of each group much in the same way is found in the 

 structure of the globiferous pedicellariæ, as emphasized by Professor D 6 d e r 1 e i n (loc. cit.). In the 

 canalifcrus-g-zow^ the valves have the terminal opening surrounded by a circle of teeth, in the fragilis- 

 group the valves end in a single, large tooth with the opening at its base on one .side; S. Philippii 

 alone makes an exception here, the valves having four teeth round the terminal opening. Professor 

 Doderlein finds the globiferous pedicellariæ of this species to belong to the aviali/enis-ty^Q; I 

 cannot quite agree with him herein, finding" those of .S'. Philippii to form a separate type. (For a more 

 detailed account thereof I must refer to the Report on the Echinoidea of the Swedish South Polar 

 Expedition). Other characters of importance distinguishing these groups I have not been able to find. 

 The latero-anal fasciole passes over the 10— iith plate of the posterior ambulacra \\\ fragilis and 

 Philippii, over the 12— I3th in canaltferus and lacunosns — but in orbignyanus it may also pass over 

 the iith plate. The first of the large subanal tubefeet is found on the 5th ambulacral plate in canali- 

 ferus and lacunosus, on the 6th in fragilis, Philippii, orbignyanus and gibbcruliis. The character taken 

 by Fourtau (Op. cit.) to distinguish the two groups, viz. the arrangement of the pores in the anterior 

 ambulacrum in a single or double series, does not hold good either. In orbignyanus, lacunosus and 

 Edivardsi they are arranged in a single series — but nobody, I think, will deny that these species 

 belong to the same group as canali/criis, which has the pores arranged in a double series. — The other 

 pedicellariæ as well as the spicules do not afford characters by which to distinguish the groups. But 

 the three characters pointed out above: the form of the test, the number of genital pores and the struc- 

 ture of the globiferous pedicellariæ agree in the most beautiful manner and show that the species 

 canaliferus, orbignyanus, Edivardsi and lacunosus form one distinct group, the species fragilis, Moscleyi, 

 antarctictis, capensis, Townsendi and latifrons another group.' — To the latter group Sch. Philippii can 

 scarcely be reckoned. It differs from the other species in having the apical system and vertex almost 

 central, the shape of the test thus differing considerably from that of the other species of Mie fragilis- 



' It may be noticed that the globiferous pedicellariæ of S'. Edzvaydsi are unknown. Those of S. Moseii-yi\ Tozvusftidi 

 and lalifyons I have exaniintd and found to be of the fragiiis-tyye. 



The IngulfExpeditioii. IV. 2. l6 



