40 THE VOYAGE OF H.M.S. CHALLENGER. 



polyps than in the foregoing species. They are longish plates, with very strongly 

 toothed edges and prickly surfaces. Their length to breadth in mm. reaches 0*28-0"l ; 

 0"1 7-0*05; 0*13-0"05. In the calyx there are transversely placed plates, with sharp, 

 bent, sometimes branched teeth on the edge, which interlock closely on opposite sides. 

 Height to breadth in mm. — 0-1-0-16; 0-12-0-2 ; 0-07-0-2. The calices have hence a 

 roughly prickly surface. 



This species leads the way to Mopsea through the formation of its axis and spicules. 



Habitat. — Kerguelen Island ; depth, 10 to 80 fathoms. 



Genus 2. Mopsea, Lamouroux. 



Mopsea, Lamx., Hist, des Polyp. coralL flexiblea, p. 465, Caen, 1816. 



Colony branched, generally in one plane. The coenenchyma is relatively thick, 

 transparent only on the lowest part of the stem. The polyps are closely crowded on the 

 stem and branches in short ascending spirals, so that at times they appear to form whorls. 

 They are club-shaped and directed obliquely inwards towards the branches. The 

 tentacles are not retractile, but in repose bend themselves together inwards over the 

 oral region. The axis consists of short calcareous and horny joints. The branches 

 originate with a horny joint from the calcareous joint of the stem, but many arise so near 

 to the edge of the calcareous joint that, owing to their growth in thickness, the horny joint 

 of the branch comes into contact with that of the stem and the branch appears to arise 

 from the horny joint. The spicules of the coenenchyma are finely spined, unsymmetrical 

 scales, which are strongly toothed at the edge, where the teeth of adjacent plates inter- 

 lock. In the polyps the plates are scale-like, placed peripherally, and cover the polyp 

 in the same manner as the tentacles. They have a strong, convex curvature on the 

 surface, which corresponds to the arching of the body of the polyp, and sharp thorns on 

 the outer surface. 



The genus Mopsea was first founded by Lamouroux.' His diagnosis is : — " Polypier 

 dendroide, a rameaux pinnes, ecorce mince, adherente, couverte de mamelons tres-petits, 

 allonges, recourbes du c6te de la tige, epars ou subverticilles." To this genus he refers 

 Mopsea verticillata = Mopsea encnnula (Ehren.), and Mopsea dichotoma (Linn.). For 

 these two also the diagnosis is quite correct. Ehrenberg (Corallenthiere d. rothen Meeres) 

 adopted the genus, but modified the diagnosis in such a way that he set forth as 

 the most important character the origin of the branches from the horny joints. This led 

 him to refer to the genus a Melithseidean, Mopsella erythrsea. Milne-Edwards (Hist. Nat. 

 des Corall.) follows the precedent of Ehrenberg. Thenceforth the position of the genus 

 Mopsea became greatly involved. Gray wrongly identified a Melithaeidean with Mopsea 

 dichotoma, Lamx., for which he creates a new genus, Mopsella, while he wiU 



■ Loc. cit. 



