DE. T. DAYIDSOX ON EECEXT BEACHIOPODA. Ill 



tate In general, the foramen is moderate and the (k'ltidia are united, but in many- 

 cases the foramen is large and the deltidia are more or less widely sejiai'ated, and the a2)ex 

 is produced. I cannot doubt the identity of T. iJulchella, Sby., Avith T. sangidnca of 

 Davidson and Chemnitz." 



JJncertcdii Species. 



03. Megerlia Willemoesi, Davidson. (Plate XIX. tigs. 23-2(5.) 

 M(>(/erlia Jll/Zemocsi, Davidson, Proc. of the Koyal Soc. vol. xxvii. p. 438, 1878. 

 Merc/eVut ii-il/cinik'si, Report on the Braeliiopoda, Vojage of H.INI.S. 'Challenger,' Zoology, vol. i. p. 51, 



pi. iv. figs. 1-3, 1880 (erroneously labelled on plate Muyasella Willemoesl). 



Shell ovate, or longitudinally oval, broadest anteriorly, tapering posteriorlv. Valves 

 moderately convex, surface smooth, white. Dorsal valve moderately convex, not quite 

 so deep as the ventral one, and somewhat flattened anteriorly so that the front line is 

 slightly depressed. Yentral valve very convex, slightly flattened along the middle and 

 especially so anteriorly. Beak produced, comparatively large and truncated by a circular 

 foramen, separated from the hinge-line by a rather wide and high deltidium. In the 

 interior of the dorsal valve tlie loop is three times attached — first to the hinge-plate, ao-ain 

 to a median si^ptum, and thirdly by perpendicular lamellye which connect the lateral 

 reflected extremities of the loop with the median septum. Length 7 lines, width 5, depth 

 4 lines. 



Hub. rive examples of this interesting species, attached to branched Polyzoa, were 

 dredged in company with Terehratula ihva by the 'Challenger' Expedition, off Twofold 

 Bay, South Australia, or between Sydney and Melbourne, in 120 fathoms. 



Ohs. I can add nothing Avith respect to this species to the description here reproduced 

 from my ' Challenger ' report. The discovery of more specimens would be desirable 

 before the species is definitely admitted. 



Subgenus Laqueus, Dall, 1870. 

 Type Laqueus californiciis, Koch, sp. 

 When proposing this subgenus, Mr. Dall published th(> following diagnosis : — 

 " Shell with the reflected portion of the loop attached by slender processes, on each 

 side, to the luunial processes, at or near the points where the two septal jn-ocesses branch 

 off to the septum. Foramen complete. It will be observed that the reflected part of 

 the loop is attached by the two (lateral) processes, not to the septum nor to tlie septal 

 processes, but to the hapmal portions of the loop (which I have termed haimal processes) ; 

 thus the two septal processes, the two lateral processes, and the 'bight' of tlie neural 

 loop, form a somewhat sinuous ring, intersected by the point of the septum, the lucmal 

 processes and the two sides of the neural loop." (Eevision of the Terebratulidic, 1870, 

 p. 123.) 



This is a very good subgenus and has been generally accepted. We are acquainted 

 with tliree recent species and a named variety *, viz. : — 



Laqueus californiais, Koeli. 



californiciis, var. vancouveriensis, Davidson. 



haqums pictus, Chemnitz. 

 ruhellus, Sowerby. 



* \_Laqueus siiffmus, Dall, is figured on PI. XIX. figs. 0, 7 h. It was subsequently placed as a synonym of L. rubcUus, 

 by Dall, but was considered by Davidson tu be the young of L. ijiciics (p. 114). — A. C] 



