69 



Fremragning paa dennes Overflade uden dog at gjennem- 

 bryde den. Hos P. pulvillus er derimod denne centrale 

 Naal ikke større eller mærkelig tykkere end de øvrige, 

 og derfor ere de coniske Fremragninger paa den ydre 

 Ryghuds Overflade her mere uregelmæssigt spredte eller 

 ikke ordnede i tydelige Rader. — De 5 perianale Paxiller 

 ere ligeledes større end hos P. pulvillus og kronede med 

 15 — 18 Naale, af hvilke de 5 — 6, som vende imod Gat- 

 boret og tjene til at understøtte den tutformige Aabning 

 i den ydre Ryghud, ere større og især meget tykkere 

 end de øvrige. 



Den ydre Ryghud indeholder, ligesom hos P. pulvil- 

 lus, ingen Kalkstykker, og dens Porer (spiracula) forholde 

 sig ogsaa ganske ligedan (se Fig. 4). 



Bespir ationsr ørene (Fig. 3, e, Fig. 8) (Hudgjellerne) ere 

 betydeligt større end hos P. pulvillus, i udstrakt Tilstand 

 3—4 Mm. (hos P. pulvillus kun 1% Mm.) høie og 1—1 V 2 

 Mm. tykke, cylindriske med afkuttet, ikke kølledannet eller 

 tykkere Top, og ikke blot denne er, som hos hin Art, besat 

 med smaa rundagtige, trinde, blindtarmformige eller indven- 

 dig hule Lappe, men disse omgive ogsaa Røret næsten helt 

 nedad til dets Basis, idet de ere stillede i Krandse rundtom. 

 Af saadanne Krandse taltes 4 eller 5, stillede omtrent i 

 lige Afstand fra hinanden, af hvilke den øverste eller paa 

 Toppen siddende bestod af talrigere, ganske tæt sammen 

 staaende Lappe (maaske er den egentlig sammensat af 

 2 Krandse), i de øvrige staa disse længere fra hinanden 

 og blive jo længere nedad imod Rørets Basis desto færre 

 i Antal. 



Madreporpladen (Fig. 6, 7) er meget stærkt hvælvet (lidt 

 mere end halvkugleformig) 5 Mm. (hos P. pulvillus 3 Mm.) 

 bred og 3 Mm. høi. Den ligner mere samme af P. militaris 

 end af P. pulvillus, idet dens Overflade er noget knudret 

 eller egentlig straaleformig ribbet. Fra Centrum af dens 

 Top udgaar nemlig straaleformigt nedad imod Basis om- 

 trent 16 Ribber, af hvilke nogle nedentil forene sig 2 og 

 2, andre eller de fleste ikke; hver af disse Ribber er 

 paa begge Sider forsynet med talrige, ophøiede, skraa, 

 parallele Striber, hvilke forene sig langs ad Ribbens op- 

 høiede Midtlinie under en spids Vinkel, hvis Top vender 

 nedad mod Basis. Madreporpladen af P. militaris viser 

 vel Antydning til lignende straaleformige Ribber, men 

 disse ere mere uregelmæssige og knudrede eller besatte 

 med smaa uregelmæssige coniske Tuberkler; hos P. pul- 

 villus har den derimod ingen Ribber, men en jævn med 

 talrige temmelig regelmæssigt ligeløbende, lidet fordybede, 

 liniedannede, mangfoldig mæandrisk bugtede Furer for- 

 synet Overflade. 



Generationsorg anerne (Fig. 2, h), hvilke hos det iagt- 

 tagne Individ ikke vare meget udviklede, havde en lig- 

 nende Form af en Drueklase og vare forøvrigt i alle Hen- 

 seender overensstemmende med samme af P. pulvillus. 



Som Følge af, at Sugefødderne hos nærværende Art 



by its extremity pushing up against the under surface of 

 the exterior dorsal cuticle, a small conical nipple or pro- 

 minence on the upper surface, yet without piercing the 

 skin. In P. pulvillus on the other hand, this central 

 needle is not larger nor appreciably thicker than the 

 others; and therefore the conical prominences on the 

 surface of the exterior dorsal skin are more irregularly 

 distributed or not arranged in distinct rows. The 5 pe- 

 rianal paxillce are likewise larger than in P. pulvillus 

 and crowned with 15 — 18 needles, of which 5 — 6 which 

 are turned towards the anus, and serve to support the 

 cup-shaped aperture in the exterior dorsal skin, are 

 larger and especially much thicker than the others. 



The exterior dorsal cuticle contains, as in P. pul- 

 villus, no calcareous corpuscles; and its pores (spira- 

 cula) are also quite similar (see fig. 4). 



The Respiratory tubes (fig. 3, e, üg. 8) (the skin-gills) 

 are considerably larger than in P. pulvillus; when ex- 

 tended 3—4 Mm. (in P. pulvillus only V/ 2 Mm.) high, 

 and 1 y a Mm. thick, cylindrical with a truncated not club- 

 formed or thicker top; and not only is this top, as in 

 the other species, covered with small roundish cylindrical 

 cæca-like or inwardly hollow lobes, but these surround 

 also the tube nearly all the way down to its base, being 

 placed in circles round about. Of such circles 4 — 5 may 

 be numbered situated at about equal distances from each 

 other; the highest of them or that placed at the top, 

 consisted of more numerous quite closely standing lobes; 

 (perhaps it is properly composed of 2 circles) in the 

 others the lobes are further from each other, and become 

 fewer in number, the further downwards towards the 

 base of the tube. 



The Madreporic body (fig. 6, 7) is veryc strongly convex 

 (rather more than semiglobular) 5 Mm. (in P. pulvillus 

 3 Mm.) broad, and 3 Mm, high. It resembles more that 

 of P. militaris than that of P. pulvillus ; its surface being 

 somewhat tuberculous or properly speaking radially rib- 

 bed. From the centre of its top there proceed radially 

 downwards towards the base about 16 ribs, of which some 

 unite themselves below, 2 and 2, while others or the most 

 of them do not; each of these ribs is on both sides fur- 

 nished with numerous raised oblique parallel stripes unit- 

 ing themselves along the elevated medial line of the rib 

 at an acute angle, and having their extremities turned 

 downwards towards the base. The madreporic body of 

 P. militaris shews indeed some indication of similar radial 

 ribs; but these are more irregular and tuberculous or 

 covered with small irregularly conical prominences; but 

 in P. pulvillus it has no ribs, having on the contrary an 

 even surface marked with numerous, rather regularly run- 

 ning, linear, slightly indented, intricately sinuous or meand- 

 ring furrows. 



The organs of generation (fig. 2. h), which in the 

 specimen observed were not much developed, had a si- 

 milar cluster-like form and were also otherwise in all 

 respects similar to those of P. pulvillus. 



In consequence of the water-feet in the present spe- 



