104 



THE VOYAGE OF H.M.S. CHALLENGER. 



apparently articulates with the second, a circumstance demonstrating that the second 

 and third are fused into one more solidly in the Macrura generally, but the most 

 singular feature is the peculiar form and proportion of the phymacerite (PL XVII. c. o.p. 

 and PI. XIX. c. o.t.). The first joint or coxa of the antennas articulates freely with the 

 metope, a circumstance that distinctly separates it from the Palinuridea, and from its inferior 

 or ventral surface a hollow calcified tubercle springs, as is common in all the Macrurous 

 types, but in this family this tubercle or phymacerite is produced to 

 a considerable length, it is turned inwards and then curves upwards 

 and presses its extremity strongly against the under surface of the 

 first antenna, where it is received into a depression. The extremity 

 of the phymacerite is closed by a membrane of delicate appearance, 

 and there seems to be no free opening ; but in a specimen of Stereo- 

 mastis suhmi that I closely and carefully examined, there appears to 

 -Phymacerite of ^ e near ^ ne cen t re a crescentic line that may be a fissure, as shown 

 in the accompanying illustration, although I could not demonstrate 

 it to be so. Around this fissure, which was situated near to one extremity, there existed, 

 parallel to the outer open margin of the tubercle, a band of more solid structure divided 

 at the top and bottom. Whether this be a kind of sphincter muscle for the purpose of 

 closing the crescentic orifice, I am not prepared to say. The margin is generally 

 fringed with more or less conspicuous hairs. 



The oral cavity is large and spacious, but capable of being entirely closed by 

 membranous tissue which forms an anterior and a posterior fleshy protuberance ; the 

 former passes under the mandibles anteriorly, and apparently fulfils the functions 



Fig. 13.- 



Stereomastis suhmi. 



Fig. 14. — PentacJieles enthrix. ' ' Mandibles, with .in- 

 terior and posterior lips. Between them the oral 

 aperture and two feeler-like appendages, mandibles 

 without palpus. Enlarged four times." From a 

 drawing and note by Willemoes-Suhm. 



Fig. 15. — Pentacheles enthrix. " One of the points of the feeler-like 

 appendages magnified Jth power. The chitin-layer is removed 

 iu order to show the reticular tissue which fills up the inner 

 structure. Three small glandular masses are shown in the 

 skin, of which no doubt others are to be found all over the 

 organ." From a drawing and note by Willemoes-Suhm. 



of a tongue and lip, and may be conveniently named the cheiloglossa, while from the 

 hinder portion of the posterior lip a membranous base with a lateral process (PI. XX. d"), 

 the metastoma, is produced on each side ; it is long, tapers to a blunt point, and 

 clasps the mandibles closely round the constriction at the base of the psalisiform blade. 



