41 8 CTENOPHORA 



which the longitudinal canals extend, are found at the aboral 

 pole. CaUia7iira has two of these processes arranged in the 

 transverse plane, and Lophoctenia has four. Callianira is found 

 in the Mediterranean and in the Atlantic from the Arctic to the 

 Antarctic waters. 



Fam. 3. Pleurobrachiidae. — The body is almost spherical 

 in form, and the eight ribs are equal in length. 



This family includes the genus Pleurohrachia, in which the 

 ribs extend for a considerable distance along the lines of longi- 

 tude of the spherical body, but do not reach either the oral or 

 the aboral areas. P. pileus is the commonest Britisli Ctenophore, 

 and may be found in shoals in May, June, and July at the 

 surface of the sea or cast up on the sand as the tide ebbs. It is 

 widely distributed in the North Atlantic waters. F. rhodopis of 

 the Mediterranean has rather shorter ribs than P. j^Heus. Two 

 new species have recently been described from the Malay 

 Archipelago.^ Hormiphora (Fig. 180, p. 413) differs from 

 Pleurohrachia in having much shorter ribs, and in possessing two 

 kinds of pinnae on the tentacles, those of the ordinary kind and 

 others much larger and sometimes palmate in character. This 

 genus has a world-wide distribution. 



In Lampetia and Euplokamis the body is more cylindrical in 

 shape than it is in the other genera, but the ribs and subjacent 

 longitudinal canals extend up to the margin of the aboral field. 

 Both these genera occur in the Mediterranean, but Lampetia is 

 also found in the Malay Archipelago. 



Order II. Lobata. 



The body is considerably flattened in the transverse plane, 

 and the sagittal areas are extended into the form of two wide 

 peristomial lobes. The oral ends of the areas between the 

 transverse and sagittal ribs are extended to form four flaps, called 

 the "auricles." There are no tentacles nor tentacle -sheaths 

 of the ordinary kind in the adult form ; but numerous tentilla, 

 similar in some respects to the pinnae of the tentacles of other 

 Ctenophora, form a fringe round the margin of the auricles and 

 the peristome. A single pair of long, filamentoiis, non-retractile 

 tentacles arise from the sides of the peristomium in Eucharis 



^ F. Mosser, " Ctenoi)horeii der Siboga Expedition," Leiden, 1903. 



