. Annual report. 1st-12th, 1867-1878. Geology. 448 GEOLOGICAL SURVEY OF THE TERRITORIES. The differential characters separating them from the Decapods or any other Malacostracous type are: 1. The loosely-attached carapace, the two halves connected by an ad- ductor muscle. 2. The movable rostrum, loosely attached to the carapace. 3. The very long and large mandibular palpus; the long, slender ap- pendage of the first inaxillee, and the very long biramous inaxillse. 4. The absence of any maxillipedes. 5. The 8 pairs of pseudophyllopod thoracic feet, not adapted for walk- ing ; the animal swimmin
. Annual report. 1st-12th, 1867-1878. Geology. 448 GEOLOGICAL SURVEY OF THE TERRITORIES. The differential characters separating them from the Decapods or any other Malacostracous type are: 1. The loosely-attached carapace, the two halves connected by an ad- ductor muscle. 2. The movable rostrum, loosely attached to the carapace. 3. The very long and large mandibular palpus; the long, slender ap- pendage of the first inaxillee, and the very long biramous inaxillse. 4. The absence of any maxillipedes. 5. The 8 pairs of pseudophyllopod thoracic feet, not adapted for walk- ing ; the animal swimming on its back. 7. No zoea-formed larva. The differential characters from the Phyllopods are the following: 1. Carapace not hinged; a rostrum present. 2. Two pairs of well-developed long and large multiarticulate anten- nae ; the hinder pair in the male longer than the 1st pair. 3. The thorax and its appendages clearly differentiated from an ab- domen. Internal organs—no functional shell gland ; no highly developed liver tubes like those of all Phyllopods; stomach and ccecal appendages (liver) entirely unlike those of Phyllopods. The nervous system is entirely unlike the Phyllopod type, and ap- proaches more the Decapod and Tetradecapod type. The resemblance to the Copepoda is in some points quite striking; this is seen in the equal size of the two pairs of antennae, in the form of the abdomen, and the two caudal appendages, as well as the spines on the hind edge of the segment, in the well-developed palpus of the man- dibles, in the absence of maxillipedes, as well as the simple reproductive glands. In short, we regard the Phyllocarida as an accelerated, prematurative type of Crustacea which became well established in the lowest Pri- mordial Period, flourishing at a time when there was no Malacostracous forms, and which culminated in the Upper Silurian Period, and became nearly extinct at the close of the Carboniferous. Judging the Phyiiocanda. gr0Up by the structure of Nebal
Size: 870px × 2871px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, bookpublishe, booksubjectgeology
