264) HENRY B. BRADY. 



continuity of the series, becomes abundantly manifest in the 

 study of the " Challenger" gatherings. Not only does the 

 passage of the non-septate Cornusjnra into the septate 

 Hinaauer become easy, through an undescribed intermediate 

 form {Hauer'ma exigua, nov.), but in one remarkable and 

 beautiful species from the deeper waters of the tropics, the 

 morphological characters of three distinct '' genera" are found 

 combined. The shells of this species commence growth in 

 piano-spiral, non-septate fashion like Cornuspira> but, after 

 a number of convolutions, become angular and septate at two 

 opposite points of the periphery, putting on a series of 

 spiroloculine chambers ; subsequently the septa become 

 more frequent and at somewhat irregular intervals, and in so 

 far assume the characters of Hauerina. For purposes of 

 nomenclature it may be assumed that the final portions 

 represent the affinities of the mature organism and Hauerina 

 inconstans seems a suitable appellation for a species Avith 

 such habits of growth. The morphological relationship 

 between Bilomlina and Sjnroloculma is already well under- 

 stood. Typically the plan of growth is the same, two cham- 

 bers on the same plane to each convolution ; but whilst 

 Bilocidina has wide, somewhat inflated segments, each of 

 which in its turn encloses all those previously formed on the 

 same side so that only two segments are visible externally, 

 SpirolocuUna has narrow, non-embracing chambers, arranged 

 alternately and symmetrically so that every segment is seen on 

 both sides of the shell. These are distinctions so generally ac- 

 cepted, and under ordinary circumstances so easily recognised, 

 that the occurrence of an occasional specimen with interme- 

 diate charaeters is of no practical inconvenience. But with the 

 Triloculine and Quinqueloculine members of the group the 

 case is far otherwise. The subdivision of the Miliolce, proposed 

 by d'Orbigny in his ' Tableau methodique de la classe des 

 Cephalopodes,'- has been employed by systematists, Avith a 

 single exception, to the present time. It contains the two fol- 

 lowing generic descriptions under the family Agathistegues. 



" Genre IIT. Triloculina. — Loges opposees sur trois cotes ; 

 la meme forme a tons les ages; trois loges apparentes." 



" Genre V. Quinqueloculina. — Loges opposees sur cinq 

 cotes ; cinq loges apparantes." 



The whole weight of the distinction embodied in these 

 definitions hangs on the words " a tons les ages," a most 



1 It is an interesting fact that Orbitolites tenuissimus, Carpenter, is some- 

 times spiral and non-septate in, its earliest stage, and in like manner, 

 amongst livaline forms, Patellina corrugata, Will. 



■ 'Annales des Sci. Nat.,' 1S2G, vol. vii, pp. 299, 301. 



