CRYPTOPHIALUS MINUTUS. 571 



the powerful muscles attached to the rostral end of the latter 

 became relaxed. Round the space where the just-mentioned 

 muscles are attached to the horny disc, a sheet of other 

 muscles radiate, a few on both sides obliquely upwards, but 

 the greater number transversely and within the first-described 

 longitudinal muscles ; they extend on both sides about half 

 round the animal. There are similar muscles in Alcippe, 

 but not extending so far round the animal. Their action 

 must be to draw the whole carapace towards the surface of 

 attachment ; the action of the longitudinal muscles being to 

 shorten it ; the orifice supported by the lateral horny bars, 

 serving as the fulcrum for the contraction of the longitudinal 

 muscles. I could not see any adductor scutorum muscle, 

 although I looked particularly under the expanded plates at 

 the ends of the lateral external horny bars. 



Body. — This is laterally compressed : it is widest and 

 thickest at the upper end, and thence tapers to the lower 

 or posterior end. The last three or four thoracic segments 

 are bent under the anterior segments, giving the whole 

 something of the appearance of certain crustaceans, divested 

 of their legs. The somewhat conical mouth, with its sin- 

 gular labrum, is very large. The body consists of eight seg- 

 ments. The first segment (fig. 5, l), or that succeeding the 

 mouth, is the seventh or last cephalic segment of the arche- 

 type crustacean ; it is the largest of all eight segments ; it is 

 joined by its dorsal surface to the carapace or external 

 covering of the animal, and the membrane with which it is 

 invested is prolonged upwards and downwards (c, c, fig. 5), 

 and so forms the inner tunic of the sack. The succeeding 

 seven segments are thoracic ; they are free, and are destitute 

 of limbs ; the articulations separating them are transverse. 

 The first and second thoracic segments give rise, on their 

 medial dorsal surfaces, each to a remarkable tapering curved 

 appendage, presently to be described. At the end of the 

 last thoracic segment, there is a minute abdomen, bearing 

 three pairs of biramous cirri. 



The Mouth consists of three pairs of organs, namely, the 

 outer maxillse, maxillae, mandibles with their palpi, and of 

 a great and very curious labrum. These organs, by the fusion 

 (as in other cirripedes) of their lower segments, form a large, 



