CEEATOMYSIS. 227 



CERATOMYSIS Fax. 



Bull. Mus. Comp. Zool., XXIV, 220, 1893. 



Integument soft and membranaceous. Cephalo-thorax robust. Carapace 

 short (leaving the last two segments of the thorax exposed), spinose; frontal 

 margin truncate, armed at the external angles with a pair of long horn-like 

 spines ; a conspicuous rounded notch near the anterior end of the lateral 

 margins, serving as an excurrent orifice from the branchial chamber. Abdo- 

 men cylindrical, spinose, sixth segment not much longer than the fifth ; 

 telson very long and narrow, truncate at the distal end, setose on both mar- 

 gins. Eyes absent, their stalks assuming the form of slender styles whose 

 tips are soft and delicate, perhaps serving as tactile organs. Peduncle of the 

 first antennae rather short, reaching only to the proximal end of the last seg- 

 ment of the peduncle of the second antennoe ; flagella much longer than the 

 peduncle, flattened and fringed with long setfe on their margins. Peduncle 

 of second antennas long and slender, distal segment the longest ; scale long 

 and very narrow, ciliate on both the internal and external borders. Mandib- 

 ular palps long, reaching some distance beyond the distal end of the pedun- 

 cle of the first antennte ; second segment longest, third segment long oval, 

 its margins ciliate. Maxillipeds devoid of exopods, but furnished with an 

 internal porrect lobe ; the fifth and sixth segments are somewhat pyriform, 

 with their inner margins protuberant and furnished with setae ; the seventh 

 or terminal segment is small and is armed with two or three stout spine-like 

 set£e. The first pair of legs or gnathopods, like the following pairs, is fur- 

 nished with long exopods ; the fourth segment, moreover, is produced on 

 the inner side to form a very long porrect lamina ; the distal segment of 

 these appendages is oval, and ciliated on the margin. The following pairs 

 of legs are long and slender, the propodites of the last three pairs indistinctly 

 segmented ; the dactyli of the second, third, and fourth pairs are short and 

 unguiform, those of the fifth, sixth, and seventh pairs long and lanceolate. 

 The first to the fifth abdominal segments bear each a pair of appendages 

 which increase in size from before backward ; these appendages are all 

 simple save the left one of the fifth pair which carries (in the unique type 

 specimen) a slender lateral bi-anch (Plate LVI., Fig. 1'^). Both branches of 

 the uropods are linear, setose on both margins, subequal in length, shorter 

 than the telson ; the outer branch is not divided by a transverse suture. 

 Seven pairs of incubatory lamellae in the female. 



