POLYCH^TA BENHAM. 85 



Genus SCIONE Holmgren.* 



SCIONE MIRABILIS Mdntosk. 



Pista mirabilis Mclntosh (1885), p. 454, pi. LI, figs. 1, 2; pi. XXVI 1 A, 

 fig. 34. 



An unnamed tube, Mclntosh (1885), Introduction, p. 10, pi. XLIX, figs. 8, 9. 

 Scione spinifera Ehlers (1908), p. 152, pi. XX, figs. 10-14. 

 Scione spinifera Gravier (1911), p. 134, pi. XII, fig. 156 (tube). 

 Scione spinifera Ehlers ( 1913), p. 561, pi. XLIV, fig. 7 (tube). 

 Scione mirabilis Ehlers (1913), p. 562. 



(Plate 9, figs. 97-100.) 



The material consists of seven individuals, two of which were still within their 

 tubes, the rest having been removed therefrom before preservation. 



The tube is nearly straight with the upper free end bent downwards as figured by 

 previous authors. One tube measures 150 mm. along the curve, the other attains a 

 length of 240 mm. ; the lower end is lacking in both, but a greater portion is absent from 

 the longer one. The tube has a cylindrical lumen, 5 mm. in diameter ; the external 

 surface is raised into four longitudinal ridges which bear the characteristic long spine-like 

 processes ; these are from 10-12 mm. in length in the upper region and decrease gradually 

 towards the lower end to 1 mm., while in the lowest quarter they are absent. 



In the upper part, for a distance of about 10-20 mm., the ridges die out and the 

 spines depart from their regular linear arrangement, becoming scattered over the surface. 

 This region is of looser texture than the lower part, there being less mud adhering to the 

 basal membrane, and consequently, too, the wall is translucent. 



Embedded in the mud wall are bundles of sponge spicules, such as Mclntosh 

 describes for Pista (Scione) mirabilis ; they are disposed circularly and closely parallel 

 to one another. They are present also in the " spines," where they are disposed length- 

 wise. On the surface of the tube wall and on the spines are various colonies of Polyzoa, 

 Hydrozoa, and a portion of what seems to be Rkabdopleura, which is unfortunately 

 poorly preserved and the polypides are either absent or indistinct. 



The complete worm removed from the smaller of the two tubes has a body length 

 of 50 mm. for 92 segments ; its breadth anteriorly is 4 mm. thence tapering to the hinder 

 end. Most of the tentacles are lacking, and the few that remain are broken. 



The largest specimen in the collection had already been removed from its tube 

 before preservation ; it is about 70 mm. in body length, to which 20 mm. is to be added 

 for the length of the tentacles ; its diameter is 7 mm., and the body contains about 90 

 segments. This specimen is twisted in the abdominal region and is somewhat soft 

 further forwards, so that these dimensions are not absolutely correct. These specimens 

 are smaller than the individual of S. spinifera measured by Ehlers. 



* tfcione ia another re ooupied name, according to Leiper. 



