36 Bulletin, Vanderlilt Marine Museum, Vol. II 



forward and slightly downward pointing tooth which has the post- 

 lateral margin carinate and on the ventral surface there is an acute, 

 down-pointed spine on each side. The fourth, fifth and sixth segments 

 are successively longer and wider, the lateral margins of the fourth 

 and fifth segments are oblique with a broad, rounded process at the 

 postlateral angle ; the sixth or longest segment has a rounded node or 

 tooth at the anterolateral angle and the posterolateral margin is exca- 

 vate and concealed beneath an ovate movable process which is attached 

 laterally to the anterior margin of the first abdominal segment. The 

 first five abdominal segments are subequal and similar, except that the 

 fifth segment is about one-eighth longer than those preceding and has 

 a short, acute tooth at its postlateral angle ; on one of the specimens 

 the longitudinal carinae of the fifth segment each terminate pos- 

 teriorly in an acute tooth as on the sixth segment. The sixth or pre- 

 telsonic segment is about half as long in the median line as the pre- 

 ceding segment with a short, acute, curved, downward and outward 

 pointing tooth at the anterolateral angle ; the lateral margin slanting 

 obliquely inward to the edge of the telson and armed with another 

 smaller, acute tooth at the postlateral angle. In addition to the carinate 

 margins there are six longitudinal carinae, the sub median and adja- 

 cent median lateral pair of which begin on the anterior part of the 

 fourth thoracic segment and extend, approximately parallel to each 

 other to the posterior margin of the sixth abdominal segment, while 

 the lower lateral pair begin on the anterior part of the first abdominal 

 segment ; all six carinae terminate posteriorly in an acute spinule or 

 tooth on, or almost on, the posterior margin of the pretelsonic segment. 

 The telson is shield-shaped with a prominent median longitudinal, 

 nodulose ridge which terminates subdistally in a small acute spine 

 pointed posteriorly and has just behind and below it a conical tooth, 

 below which the telson is depressed. There is a narrow, slit-like sinus 

 in the median line of the posterior margin and on either side of it the 

 margin is rounded into a broad tooth, above which there is a single 

 nodular denticle and which is followed on the margin by a smaller 

 rounded tooth which is immediately adjacent to a longer, pointed, 

 spinose tooth from the base of which there extends inward towards the 

 median ridge a curved row of four rounded tubercles on each side. 

 There are four rounded teeth of unequal sizes each with a rounded 

 nodular tubercle at its base, between this submedian spinose tooth 

 and the next acute spinose tooth which has a short granulosa carina 

 running in from its base for a short distance, and which is separated 



