RECENT BRITISH OSTRACODA. 



3G3 



Monoculi 



ruber, Idem, ibidem, p. 172, pi. xviii. figs. 3, 4. 



Valves oblong, subreniform, narrowed in front. Anterior extremity narrow, bordered 

 by a flattened encircling lamina ; posterior broad and well rounded. Tin* ventral margin 

 is straight or slightly sinuated ; the dorsal arched, highest at its posterior third. Seen 

 from above, the carapace is oblong, ovate, tapering to the anterior extremity, which i^ 

 acutely pointed, the right valve being considerably overlapped by the left. Front view 

 ovate, the suddenly compressed anterior margins projecting sharply forward. The surface 

 is indistinctly granular, and finely punctate. Colour ochreous yellow, marked with 

 bands and blotches of deeper orange. Near the anterior third of the dorsum there is 

 frequently a conspicuous deep-brown or black spot, marking probably the position of the 

 eye. The arrangement of the antennal setse is precisely like that of C. virens,—tlic upper 

 antenna bearing nine long and several shorter plumose filaments ; the lower five, which 

 reach but slightly beyond the apices of the claws. Four much shorter and mosth 

 non-plumose setse rise from the middle of the fourth joint, and reach not very much 

 beyond the bases of the claws. These are found in all members of the genus. Setae of 

 the abdominal rami four, the two shorter ones being much longer than those of C.fuacc 

 or 0. virens. The anterior portion of the shell is not unfrequently studded with I 

 number of minute tubercles, which along the margin are gathered into a regular row 

 of from twenty to thirty (fig. 21), producing an appearance as of a finely crcnatcd or 

 serrated border. The marginal row of tubercles is present, however, only on the right or 

 smaller valve, which is provided internally with a narrow laminar plate (fig. 22), and is 

 received within the overlapping and perfectly simple margin of the left valve. The pos- 

 terior margin is also occasionally, but less frequently, tuberculated in a similar manner. 



Length ■][} in., height -£$ in. 



0. incongruens seems to be one of the less common species of this genus, it na* 

 been found in Kent and Essex by Professor T. Rupert Jones, at Blaekheath, % indsor 

 and Dover by Dr. Baird, in the island of Cumbrae and in a lagoon on the Ayrshire coas 

 by Mr. D. Itobertson, in the county of Durham and in the Isle of Arranmore (Ga way) 

 by myself. It has a wide range on the continent, being mentioned by various authors 

 as occurring in Switzerland, Germany, Norway, and Sweden „„„„„; ni ^ 



My figures and description of this species were completed be ore I became acquainted 

 with the" memoir of Eifcher contained in the < *-^£Z?££S& 

 and it is satisfactory to find that the fr*"*"* ■**£»£ £^ however> 



eharacters of O. aurantia are quite » ^J^^Zhe ground of the want of 

 assigns a specific rank to C. rubra, Junne almost en nely on t .^^ 



tuberculatum of the carapace, at the same time admi tang £ *£ *£ J for from 

 ption, and that the relations between C. ££«<■£ ^ % be seen that , regard 

 being clearly made out •. Erom what has been said » ' , but 



the two former species as distinct, not only from characters afforded by t P 



h nicht Uebergangsformen aradien C. aurantia , futca und 

 * Es muss ubrisens erst weitere Beobachtung lebreri, oo Kurperbau durchaus kerne wesenl- 



7*. stattuoden, und sie alle drei uur * eh* Species zu betraehteu surd, da 

 Uche Verschiedenheit wahrnehmen liisst." 3 D 2 



