REPORT ON THE SIPHON OPHOR^E. 163 



is far larger and subcircular. The ventral margin of the latter is cleft in its middle ; the 

 large dentate plate arising from the right ventral crest of the basal nectophore here 

 covers, like a valve, the free margin of the smaller plate which arises from the opposite 

 left crest (figs. 3, 9, uk). 



The Siphosome, which arises in the apex of the hydrcecium of the apical nectosac, 

 enters into the hydroecial canal of the basal nectosac by its apical aperture, runs through 

 it along the ventral face of the nectosac, and proceeds freely through its basal aperture 

 (fig. 1). In its contracted state, however, the retracted siphosome is completely hidden 

 in the hydroecial canal (fig. 2). 



Cormidia. — The numerous cormidia, which are attached to the stem of the siphosome, 

 are separated by regular free internodes, and become mature in the form of free Eudoxiae, 

 which belong to the monogastric genus Sphenoides (compare Genus 15 and PL XXXYIIL). 

 These are characterised by the peculiar wedge-form of their bracts, and mainly by 

 the odd spur-shaped dorsal canal, which descends from the base of the large ovate 

 phyllocyst downwards. 



Genus 31. Calpe, 1 Quoy et Gaimard, 1827. 

 Calpe, Quoy et Gaimard, Ann. d. Sci. Nat., 1827, t. x. p. 11. 



Definition. — Diphyiclse with two angular, pyramidal or prismatic nectophores of 

 different size and unequal form. The basal nectophore is five-sided pyramidal, asym- 

 metrical, and much larger than the symmetrical apical nectophore. Bracts cuboidal, 

 with a five-sided pyramidal apophysis, and a vesicular phyllocyst, from the base of which 

 four canals arise, two slender odd sagittal and two broader paired lateral canals 

 (Aglaisma, Genus 16). 



The genus Calpe was founded by Quoy and Gaimard in 1827 for the well-known 

 Mediterranean species Calpe pentagona. Eschscholtz (1, p. 132), and the majority of 

 later authors, have described this striking form under the name Abyla pentagon// 

 (Kolliker 4, Leuckart 5, Huxley 9, Gegenbaur 10, &c). But, besides the other char- 

 acters, the pentagonal form of the distal nectophore distinguishes the true Calpe at once 

 from the trigonal Abyla and the tetragonal Bassia, and stdl more the different form of 

 the bracts in these three genera of Abylidae. The phyllocyst of the true Calpe gives off 

 four radial canals, two of which are odd and slender (an ascending and a descending), 

 and two others paired and lateral. The free Eudoxia belongs to the monoirastric senus 

 Aglaisma (Genus 16). It was in this genus that Leuckart (5) and Gegenbaur (7), both 

 independently, at the same time, observed the detachment of free Eudoxiae from the 

 Diphyid corm (compare above, p. 90). 



The new species of Calpe, described in the following as Calpe gegenbauri, inhabits 



1 Calpe = ~\jTn, KaA^n; also the northern column of Hercules, opposite to Abyla, Strait of Gibraltar. 



