On the structure, biology and systematic position ofPharus legumen(L.)

Abstract

The species with which this paper deals was originally included by Linne in the genus Solen and was there retained to be included under that name in the magnificently illustrated account of this genus by Deshayes (1845–48). It was later placed in a new genus Ceratisolen by Forbes & Hanley (1853) who considered that it formed ‘the connecting link between the Solenidae and Solecurtidae’. This procedure was followed by Jeffreys (1865). More recently the Solecurtidae were shown by Graham (1934b) having ‘regard to such features as shape, presence of a cruciform muscle and the structure of the foot, siphons, adductor and pedal muscles, supra-axial extension of the outer demibranch, palps, and style-sac and intestine’, to belong to the Tellinacea, a view fully supported by this author (Yonge, 1949). Assigned later to the genus Pharus which has priority over Ceratisolen, this ‘connecting link’ of Forbes & Hanley continued to be associated with the Solenacea by Thiele (1935) in his great systematic account of the Mollusca.

The functional morphology of Sinonovacula constricta with a discussion on the taxonomic status of the Novaculininae (Bivalvia).

“…Thus in the mid-line there is a small inverted "V" of tissue that represents the left and right outer surfaces of the middle folds (FMMF). A similar situation occurs in Pharella (Solenacea) (Owen, 1959) and in Pharus (Tellinacea) (Yonge, 1959). The outer folds (OMF) are here greatly enlarged forming a capacious haemocoel latero-ventrally.…”

“…6(a)) the siphons comprise simple tubes with the inner epithelium of both pleated into eight folds each containing a nerve leading to the tentacles of the siphonal crown. In the Tellinacea, there are six nerves in each siphon (Yonge, 1949; though in Pharus which Yonge (1959) places in the Tellinacea (from the Solenacea) there are eight. Similarly, members of the Donacidae seem to be an exception with Egeria and Iphigenia possessing six nerves in the inhalant siphon and eight in the exhalant siphon (Purchon, 1963;Narchi, 1972).…”

“…The deep burrowing bivalve lineages Tellinacea and Solenacea are clearly closely related (Keen, 1969a; but probably because of convergent evolution, differences between the two are masked by apparently similar adaptations to similar habits. Thus Yonge (1959) transferred Pharus legurnen from the Solenacea to the Tellinacea, and Owen (1959) transferred the Glaucomyidae (Glauconomidae) (Keen, 19694 from the Solenacea to the Veneracea, thereby demonstrating that the Tellinacea and Solenacea are not the only confusing deep burrowers.…”

Sperm ultrastructure in Hemidonax pictus (Hemidonacidae, Bivalvia, Mollusca): comparison with other heterodonts, especially Cardiidae, Donacidae and Crassatelloidea

“…Whereas it is true that shell microstucture has proven a very valuable source of characters for phylogenetic analysis, Schneider & Carter (2001) have not offered any explanation for the key anatomical differences between Hemidonax and the Tellinoidea, particularly the absence of the cruciform muscle (its presence is a synapomorphy of the Tellinoidea – see also Boss, 1971, 1982). In this connection it is worth noting that Pharus and the Novaculininae (both originally included in Solecurtidae) were often cited as tellinoidean taxa lacking a cruciform muscle (Yonge, 1949, 1959; Ponder et al ., 1981; Boss, 1982) but are now both placed within the Solenoidea (e.g. Morton, 1984; von Cosel, 1990; Willan, 1998).…”

Treatise Online no. 48: Part N, Revised, Volume 1, Chapter 31: Illustrated Glossary of the Bivalvia

“…84). This muscle associates with paired sensory organs believed to monitor water quality (Morse, 1913;yoNGe, 1959). The cruciform muscle makes a pair of small attachment scars near the posteroventral shell margin, e.g., in Tellinidae (see Fig.…”