52 Description of Genera and Sj^ecies. 



There are no longitudinal keels, and there appear to be no spines even upon the hind- 

 most segments ; but this is difficult to say with certainty on account of the wrinkled 

 character of the test. The telson, to judge from the part preserved, is of the usual 

 type, but the cordate body of it appears to be shorter relatively to the terminal spine 

 than in the other described species. The spine is continuous with a raised or embossed 

 ridge on the body, and moderately large accessory flattened swimmerets are articulated 

 with the body at the base of the spine. 



Neither the eyes and antennules, nor the antenna have been observed, as the 

 specimen is evidently broken away where they might be expected to occur. The 

 position of the body of the mandible is shown in the usual manner by the collapsed 

 carapace. The maxill£e and the maxillipedes are unknown. The massive legs are 

 folded up and huddled together, and closely pressed to the sternum as usual, 

 thus following the upward bend of this part of the trunk. They are seen to flex 

 at articulations corresponding with those in other species, the proximal joints flexing 

 forwards and the distal ones in the opposite direction. The long joint is comparatively 

 longer and straighter than in the other forms. What appears to be the tip of the 

 exopodites is seen bending backwards and upwards from the elbow-joints of the 

 folded-up endopodites. A point of the greatest morphological interest, however, is that, 

 articulated with the sternites of the two last trunk segments, there are large bag-like 

 structures identical in character with the marsupium of certain Mysid forms. In 

 their compressed state they appear as leaf-shaped plates, each with narrow articulations, 

 suddenly expanding beyond the articulation, with concave margin on one side and 

 convex on the other, the two sides slightly converging and meeting in a rounded tip. 

 A sht or invagination proceeding from about the mid-line of the plate, a little below the 

 point of articulation, traverses the rest of the plate with nearly the same curve as the 

 concave margin, but converging gently with it, and meets it near the beginning of the 

 rounding of the tip. This slit does not expose the underlying shaly matrix, and is 

 therefore either an invagination of the exposed side of the plate or else the plate is 

 double, which probably is the case. A detached organ of similar character, but of 

 somewhat more elongated form, is seen to occur among the disjecta membra of 

 one of the specimens of P. elegans (fig. 2^^), and shown on figs. 2 and 2^ There can 

 remain little doubt, therefore, that these forms are correctly placed among the opossum- 

 shrimps. 



Remarks. — This specific name is given to associate this form with that of the late 

 Mr. Andrew Patton, Manager of the Calderwood Cement Works, East Kilbride, Lanark- 

 shire, to whom we are indebted for collecting not only this most interesting crustacean, 

 but also other arthropods new to science. 



